cos x = 1 / (sec x) Cosine Formulas Using Pythagorean Identity. One of the trigonometric identities talks about the relationship between sin and cos. It says, sin 2 x + cos 2 x = 1, for any x. We can solve this for cos x. Consider sin 2 x + cos 2 x = 1. Subtracting sin 2 x from both sides, cos 2 x = 1 - sin 2 x. Taking square root on both sides ... Jun 24, 2016 · This can be done by the useful technique of differentiating under the integral sign. In fact, this is exercise 10.23 in the second edition of "Mathematical Analysis" by Tom Apostol. Free math problem solver answers your algebra, geometry, trigonometry, calculus, and statistics homework questions with step-by-step explanations, just like a math tutor. Dec 23, 2021 · Notice, the reciprocal trigonometric identities give that sec(x) = 1/cos(x), and the derivatives of trigonometric functions give that the derivative of sec(x) is sec(x)tan(x). All together, we ... Free math problem solver answers your algebra, geometry, trigonometry, calculus, and statistics homework questions with step-by-step explanations, just like a math tutor. The equation is. cosx − 1 = − cosx. ⇒, 2cosx = 1. ⇒, cosx = 1 2. The solutions are. {x = π 3 + 2kπ x = 5 3π +2kπ, ∀k ∈ Z. Answer link.Free trigonometric equation calculator - solve trigonometric equations step-by-step What is the formula of (1 - cos x) / sin x? Solution: As we know that (1 - cos x) = 2sin 2 (x/2) and sin x = 2sin (x/2).cos (x/2) (1 - cos x) = 2sin 2 (x/2) ---- (1 ... May 29, 2023 · Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class. Book a free demo. Transcript. Show More. Next: Ex 7.3, 10 Important → Ask a doubt (cotx)2 +1 = (cosecx)2 Odd and even properties cos( x) = cos(x) sin( x) = sin(x) tan( x) = tan(x) Double angle formulas sin(2x) = 2sinxcosx cos(2x) = (cosx)2 (sinx)2 cos(2x) = 2(cosx)2 1 cos(2x) = 1 2(sinx)2 Half angle formulas sin(1 2 x) 2 = 1 2 (1 cosx) cos(1 2 x) 2 = 1 2 (1+cosx) Sums and di erences of angles cos(A+B) = cosAcosB sinAsinB cos ...Compute answers using Wolfram's breakthrough technology & knowledgebase, relied on by millions of students & professionals. For math, science, nutrition, history ...Graph y=cos(x-1) Step 1. Use the form to find the variables used to find the amplitude, period, phase shift, ... Step 6.5.1. Replace the variable with in the expression. cos( ) = x 1 = x sec( ) = 1 x tan( ) = y x cot( ) = x y FactsandProperties Domain Thedomainisallthevaluesof thatcanbe pluggedintothefunction. sin( ), canbeanyangleAug 14, 2015 · 1 Answer. Chandra S. Aug 14, 2015. cos x = - 1/2 = cos 2 π /3 ⇒ x = 2 π /3. Free trigonometric equation calculator - solve trigonometric equations step-by-stepOct 3, 2016 · Multiply by 1 + cosx 1 + cosx to get. 1 − cos2x x(1 + cosx) = sin2x x(1 +cosx) = sinx ⋅ sinx x ⋅ 1 1 + cosx. Taking the limit as x → 0 gives. (0)(1)(1 2) = 0. Answer link. Free math problem solver answers your algebra, geometry, trigonometry, calculus, and statistics homework questions with step-by-step explanations, just like a math tutor.Sep 19, 2017 · Explanation: since cosx > 0. then x will be in the first/fourth quadrants. cosx = 1 2. ⇒ x = cos−1(1 2) = π 3 ← angle in first quadrant. or x = (2π − π 3) = 5π 3 ← angle in fourth quadrant. Answer link. Free trigonometric equation calculator - solve trigonometric equations step-by-stepPrecalculus. Solve for x 2cos (x)-1=0. 2cos (x) − 1 = 0 2 cos ( x) - 1 = 0. Add 1 1 to both sides of the equation. 2cos(x) = 1 2 cos ( x) = 1. Divide each term in 2cos(x) = 1 2 cos ( x) = 1 by 2 2 and simplify. Tap for more steps... cos(x) = 1 2 cos ( x) = 1 2. Take the inverse cosine of both sides of the equation to extract x x from inside ...Mathematically, it is written as cos-1 (x) and is the inverse function of the trigonometric function cosine, cos(x). An important thing to note is that inverse cosine is not the reciprocal of cos x. There are 6 inverse trigonometric functions as sin-1 x, cos-1 x, tan-1 x, csc-1 x, sec-1 x, cot-1 x.Compute answers using Wolfram's breakthrough technology & knowledgebase, relied on by millions of students & professionals. For math, science, nutrition, history ...Free Pre-Algebra, Algebra, Trigonometry, Calculus, Geometry, Statistics and Chemistry calculators step-by-stepThe equation is. cosx − 1 = − cosx. ⇒, 2cosx = 1. ⇒, cosx = 1 2. The solutions are. {x = π 3 + 2kπ x = 5 3π +2kπ, ∀k ∈ Z. Answer link.Compute answers using Wolfram's breakthrough technology & knowledgebase, relied on by millions of students & professionals. For math, science, nutrition, history ...Sep 19, 2017 · Explanation: since cosx > 0. then x will be in the first/fourth quadrants. cosx = 1 2. ⇒ x = cos−1(1 2) = π 3 ← angle in first quadrant. or x = (2π − π 3) = 5π 3 ← angle in fourth quadrant. Answer link. Explanation: Use the identity: secx = 1 cosx. 1 secx = 1 1 cosx = 1 ⋅ cosx 1 = cosx. Answer link.Jan 31, 2017 · 1. Hint The appearance of 1 + cos x 1 + cos x suggests we can produce an expression without a constant term in the denominator by substituting x = 2t x = 2 t and using the half-angle identity cos2 t = 12(1 + cos 2t) cos 2 t = 1 2 ( 1 + cos 2 t). Share. Arccos. Arccosine, written as arccos or cos -1 (not to be confused with ), is the inverse cosine function. Both arccos and cos -1 are the same thing. Cosine only has an inverse on a restricted domain, 0 ≤ x ≤ π. In the figure below, the portion of the graph highlighted in red shows the portion of the graph of cos (x) that has an inverse. cos^-1(x) Natural Language; Math Input; Extended Keyboard Examples Upload Random. Compute answers using Wolfram's breakthrough technology & knowledgebase, relied on ... The following (particularly the first of the three below) are called "Pythagorean" identities. sin 2 ( t) + cos 2 ( t) = 1. tan 2 ( t) + 1 = sec 2 ( t) 1 + cot 2 ( t) = csc 2 ( t) Advertisement. Note that the three identities above all involve squaring and the number 1. You can see the Pythagorean-Thereom relationship clearly if you consider ...Arccos. Arccosine, written as arccos or cos -1 (not to be confused with ), is the inverse cosine function. Both arccos and cos -1 are the same thing. Cosine only has an inverse on a restricted domain, 0 ≤ x ≤ π. In the figure below, the portion of the graph highlighted in red shows the portion of the graph of cos (x) that has an inverse.clc clear close all syms x f(x) = (cos(x))*(cosh(x))+1; fplot(x,f) xlim([0 10]); ylim([-100 100]); Why is the gragh cut off??Fleur Jul 5, 2017 graph{cos x + 1 [-10, 10, -5, 5]} If you graph the function, you can see that the domain includes all real numbers, and the range includes all values from 0 to 2, ...In y = cos(x), the center is the x-axis, and the amplitude is 1, or A=1, so the highest and lowest points the graph reaches are 1 and -1, the range of cos(x). Compared to y=cos(x), shown in purple below, the function y=2 cos(x) (red) has an amplitude that is twice that of the original cosine graph.Precalculus. Solve for x 2cos (x)-1=0. 2cos (x) − 1 = 0 2 cos ( x) - 1 = 0. Add 1 1 to both sides of the equation. 2cos(x) = 1 2 cos ( x) = 1. Divide each term in 2cos(x) = 1 2 cos ( x) = 1 by 2 2 and simplify. Tap for more steps... cos(x) = 1 2 cos ( x) = 1 2. Take the inverse cosine of both sides of the equation to extract x x from inside ...Use the form asec(bx−c)+ d a sec ( b x - c) + d to find the variables used to find the amplitude, period, phase shift, and vertical shift. a = 1 a = 1. b = 1 b = 1. c = 0 c = 0. d = 0 d = 0. Since the graph of the function sec s e c does not have a maximum or minimum value, there can be no value for the amplitude. Amplitude: None. Apr 12, 2016 · sin2x +cos2x = 1. where we can subtract cos2x from both sides to get what we have in blue above: sin2x = 1 − cos2x. Thus, this expression is equal to. sin2x. All we did was use the difference of squares property to our advantage, recognize that the expression we had is derived from the Pythagorean Identity, use it, and simplify. Hope this helps! קוסינוס (מסומן ב- ) היא פונקציה טריגונומטרית בסיסית, המתאימה לכל זווית מספר ממשי בין (1-) ל-1. הרחבות שונות של הפונקציה משמשות במגוון תחומים, כגון: הגדרות שונות ב אנליזה (ובפרט ב אנליזה מרוכבת ...Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class. Book a free demo. Transcript. Show More. Next: Ex 7.3, 10 Important → Ask a doubtSine and Cosine Laws in Triangles. In any triangle we have: 1 - The sine law. sin A / a = sin B / b = sin C / c. 2 - The cosine laws. a 2 = b 2 + c 2 - 2 b c cos A. b 2 = a 2 + c 2 - 2 a c cos B. c 2 = a 2 + b 2 - 2 a b cos C.Free math problem solver answers your algebra, geometry, trigonometry, calculus, and statistics homework questions with step-by-step explanations, just like a math tutor. Jul 24, 2018 · The equation is. cosx − 1 = − cosx. ⇒, 2cosx = 1. ⇒, cosx = 1 2. The solutions are. {x = π 3 + 2kπ x = 5 3π +2kπ, ∀k ∈ Z. Answer link. Introduction to Trigonometric Identities and Equations; 7.1 Solving Trigonometric Equations with Identities; 7.2 Sum and Difference Identities; 7.3 Double-Angle, Half-Angle, and Reduction FormulasFree trigonometric equation calculator - solve trigonometric equations step-by-step Jun 24, 2016 · Hero and Nghi, I think I could invoke more interest by including the. solutions for cosx − sinx = 1, and for that matter, secx ± tanx = 1, that become. cosx − sinx = 1 and cosx +sinx = 1, upon multiplication by. cos x, when x ≠ an odd multiple of π 2. For cos x - sin x = 1, the general solution is. x = 2nπ and x = (4n − 1) π 2,n = 0 ... Use the identity: cos (a + b) = cos a.cos b - sin a.sin b cos 2x = cos (x + x) = cos x.cos x - sin x. sin x = cos^2 x - sin^2 x = = cos^2 x - (1 - cos^2 x) = 2cos ^2 ...My origin equation is 2 x^2 (-1 + Cos[x] Cosh[x]) == 0, how could I know I should first divide the equation by x^2, before applying your code on big x approximation.Arccos. Arccosine, written as arccos or cos -1 (not to be confused with ), is the inverse cosine function. Both arccos and cos -1 are the same thing. Cosine only has an inverse on a restricted domain, 0 ≤ x ≤ π. In the figure below, the portion of the graph highlighted in red shows the portion of the graph of cos (x) that has an inverse. Misc 16 Find the derivative of the following functions (it is to be understood that a, b, c, d, p, q, r and s are fixed non-zero constants and m and n are integers ...Cos x = -1. Cách giải phương trình cos x = a (*) B. Phương trình lượng giác thường gặp. Cách giải phương trình lượng giác cơ bản đưa ra phương pháp và các ví dụ cụ thể, giúp các bạn học sinh THPT ôn tập và củng cố kiến thức về dạng toán hàm số lượng giác 12. Tài liệu ...Integral 1/(cos(x) - 1)Nice integral using trig identities.Compute answers using Wolfram's breakthrough technology & knowledgebase, relied on by millions of students & professionals. For math, science, nutrition, history ...Free math problem solver answers your algebra, geometry, trigonometry, calculus, and statistics homework questions with step-by-step explanations, just like a math tutor. 1-cos^{2}x. en. Related Symbolab blog posts. Practice, practice, practice. Math can be an intimidating subject. Each new topic we learn has symbols and problems we ...What is the formula of (1 - cos x) / sin x? Solution: As we know that (1 - cos x) = 2sin 2 (x/2) and sin x = 2sin (x/2).cos (x/2) (1 - cos x) = 2sin 2 (x/2) ---- (1 ... We would like to show you a description here but the site won’t allow us. We would like to show you a description here but the site won’t allow us.Aug 14, 2023 · What is tan 30 using the unit circle? tan 30° = 1/√3. To find this answer on the unit circle, we start by finding the sin and cos values as the y-coordinate and x-coordinate, respectively: sin 30° = 1/2 and cos 30° = √3/2. Now use the formula. Recall that tan 30° = sin 30° / cos 30° = (1/2) / (√3/2) = 1/√3, as claimed. What is the formula of (1 - cos x) / sin x? Solution: As we know that (1 - cos x) = 2sin 2 (x/2) and sin x = 2sin (x/2).cos (x/2) (1 - cos x) = 2sin 2 (x/2) ---- (1 ... Jan 31, 2017 · 1. Hint The appearance of 1 + cos x 1 + cos x suggests we can produce an expression without a constant term in the denominator by substituting x = 2t x = 2 t and using the half-angle identity cos2 t = 12(1 + cos 2t) cos 2 t = 1 2 ( 1 + cos 2 t). Share. Graph y=cos(x-1) Step 1. Use the form to find the variables used to find the amplitude, period, phase shift, and vertical shift. Step 2. Find the amplitude . Amplitude:Explanation: In the trigonometric circle you will notice that cos (x)=0 corresponds to x = π 2 and also x = − π 2. Additionally to these all the angles that make a complete turn of the circle ( 2kπ) plus ± π 2 correspond to cos (x)=0. So you have: x = ± π 2 +2kπ,k ∈ Z. If you try to see which are the first elements (from k =0, 1,2 ...Solve for x cos(x)(cos(x)-1)=0. Step 1. If any individual factor on the left side of the equation is equal to , the entire expression will be equal to . Step 2.Arccos. Arccosine, written as arccos or cos -1 (not to be confused with ), is the inverse cosine function. Both arccos and cos -1 are the same thing. Cosine only has an inverse on a restricted domain, 0 ≤ x ≤ π. In the figure below, the portion of the graph highlighted in red shows the portion of the graph of cos (x) that has an inverse.We would like to show you a description here but the site won’t allow us.Graph y=cos(x) Step 1. Use the form to find the variables used to find the amplitude, period, phase shift, and vertical shift. Step 2. Find the amplitude . Amplitude:First of all, note that implicitly differentiating cos(cos−1x)= x does not prove the existence of the derivative of cos−1 x. What it does show, however, ... By definition we have that for x ∈ [0,2π] for 0 ≤ x≤ π cos−1 cosx = x for π< x ≤ 2π cos−1 cosx = 2π−x and this is periodic with period T = 2π. Thus it ... What is the formula of (1 - cos x) / sin x? Solution: As we know that (1 - cos x) = 2sin 2 (x/2) and sin x = 2sin (x/2).cos (x/2) (1 - cos x) = 2sin 2 (x/2) ---- (1 ...cos^2 x + sin^2 x = 1. sin x/cos x = tan x. You want to simplify an equation down so you can use one of the trig identities to simplify your answer even more. some other identities (you will learn later) include -. cos x/sin x = cot x. 1 + tan^2 x = sec^2 x. 1 + cot^2 x = csc^2 x. hope this helped! First of all, note that implicitly differentiating cos(cos−1x)= x does not prove the existence of the derivative of cos−1 x. What it does show, however, ... By definition we have that for x ∈ [0,2π] for 0 ≤ x≤ π cos−1 cosx = x for π< x ≤ 2π cos−1 cosx = 2π−x and this is periodic with period T = 2π. Thus it ... Trigonometry Solve for ? cos (x)=-1 cos (x) = −1 cos ( x) = - 1 Take the inverse cosine of both sides of the equation to extract x x from inside the cosine. x = arccos(−1) x = arccos ( - 1) Simplify the right side. Tap for more steps... x = π x = π The cosine function is negative in the second and third quadrants. False due to a clash of conventions. If n > 1 is a positive integer, then: cos^n x = (cos x)^n This is a convenience of notation, to avoid having to use parentheses to distinguish, for example: (cos x)^2 and cos (x^2) By convention we can write: cos^2 x and cos x^2 respectively, without ambiguity. However, in the case of -1, we have a clash of notation. If f(x) is a function, then f^(-1)(x) is ...Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class. Book a free demo. Transcript. Show More. Next: Ex 7.3, 10 Important → Ask a doubtFleur Jul 5, 2017 graph{cos x + 1 [-10, 10, -5, 5]} If you graph the function, you can see that the domain includes all real numbers, and the range includes all values from 0 to 2, ...lim_(x->0) (cos(x)-1)/x = 0. We determine this by utilising L'hospital's Rule. To paraphrase, L'Hospital's rule states that when given a limit of the form lim_(x→a)f(x)/g(x), where f(a) and g(a) are values that cause the limit to be indeterminate (most often, if both are 0, or some form of ∞), then as long as both functions are continuous and differentiable at and in the vicinity of a, one ...1-cos^{2}x. en. Related Symbolab blog posts. Practice, practice, practice. Math can be an intimidating subject. Each new topic we learn has symbols and problems we ...Free trigonometric equation calculator - solve trigonometric equations step-by-stepIn y = cos(x), the center is the x-axis, and the amplitude is 1, or A=1, so the highest and lowest points the graph reaches are 1 and -1, the range of cos(x). Compared to y=cos(x), shown in purple below, the function y=2 cos(x) (red) has an amplitude that is twice that of the original cosine graph.Sep 19, 2017 · Explanation: since cosx > 0. then x will be in the first/fourth quadrants. cosx = 1 2. ⇒ x = cos−1(1 2) = π 3 ← angle in first quadrant. or x = (2π − π 3) = 5π 3 ← angle in fourth quadrant. Answer link. Pythagorean identities Trigonometric functions and their reciprocals on the unit circle. All of the right-angled triangles are similar, i.e. the ratios between their corresponding sides are the same. For sin, cos and tan the unit-length radius forms the hypotenuse of the triangle that defines them.Aug 14, 2015 · 1 Answer. Chandra S. Aug 14, 2015. cos x = - 1/2 = cos 2 π /3 ⇒ x = 2 π /3. Mar 16, 2020 · how to plot cosx*coshx+1=0. Learn more about cosxcosh+1=0, plot clc clear close all syms x f(x) = (cos(x))*(cosh(x))+1; fplot(x,f) xlim([0 10]); ylim([-100 100]); Why is the gragh cut off?? Compute answers using Wolfram's breakthrough technology & knowledgebase, relied on by millions of students & professionals. For math, science, nutrition, history ... Free trigonometric equation calculator - solve trigonometric equations step-by-step Aug 14, 2023 · What is tan 30 using the unit circle? tan 30° = 1/√3. To find this answer on the unit circle, we start by finding the sin and cos values as the y-coordinate and x-coordinate, respectively: sin 30° = 1/2 and cos 30° = √3/2. Now use the formula. Recall that tan 30° = sin 30° / cos 30° = (1/2) / (√3/2) = 1/√3, as claimed. Jan 31, 2017 · 1. Hint The appearance of 1 + cos x 1 + cos x suggests we can produce an expression without a constant term in the denominator by substituting x = 2t x = 2 t and using the half-angle identity cos2 t = 12(1 + cos 2t) cos 2 t = 1 2 ( 1 + cos 2 t). Share. May 4, 2018 · Explanation: since cosx < 0 then x is in second/third quadrants. x = cos−1( 1 √2) = π 4 ← related acute angle. ⇒ x = π− π 4 = 3π 4 ← second quadrant. or x = π+ π 4 = 5π 4 ← third quadrant. due to the periodicity of the cosine the solutions will. repeat every 2π. solutions are. x = 3π 4 +2nπ → (n ∈ Z)
Graph y=cos(x)-1. Step 1. Use the form to find the variables used to find the amplitude, period, phase shift, and vertical shift. Step 2. Find the amplitude . Amplitude:. Frigidaire stackable washer and dryer clean lint filter light
2cos(x)sin(x) Which we can say it's a sum. cos(x)sin(x) + sin(x)cos(x) Which is the double angle formula of the sine. cos(x)sin(x) + sin(x)cos(x) = sin(2x) But since we multiplied by 2 early on to get to that, we need to divide by two to make the equality, so. cos(x)sin(x) = sin(2x) 2. Answer link.The inverse of sine is denoted as arccos or cos-1 x. For a right triangle with sides 1, 2, and √3, the cos function can be used to measure the angle. In this, the cos of angle A will be, cos(a)= adjacent/hypotenuse. Multiply by 1 + cosx 1 + cosx to get. 1 − cos2x x(1 + cosx) = sin2x x(1 +cosx) = sinx ⋅ sinx x ⋅ 1 1 + cosx. Taking the limit as x → 0 gives. (0)(1)(1 2) = 0. Answer link.Free math problem solver answers your algebra, geometry, trigonometry, calculus, and statistics homework questions with step-by-step explanations, just like a math tutor.2cos(x)sin(x) Which we can say it's a sum. cos(x)sin(x) + sin(x)cos(x) Which is the double angle formula of the sine. cos(x)sin(x) + sin(x)cos(x) = sin(2x) But since we multiplied by 2 early on to get to that, we need to divide by two to make the equality, so. cos(x)sin(x) = sin(2x) 2. Answer link.The first step is to multiply the two expressions between parentheses : (II) There is a trigonometric identity that states : Working with this expression : ⇒. (I) Using the equation (I) in (II) : ⇒. arrow right.2cos(x)sin(x) Which we can say it's a sum. cos(x)sin(x) + sin(x)cos(x) Which is the double angle formula of the sine. cos(x)sin(x) + sin(x)cos(x) = sin(2x) But since we multiplied by 2 early on to get to that, we need to divide by two to make the equality, so. cos(x)sin(x) = sin(2x) 2. Answer link.Free math problem solver answers your algebra, geometry, trigonometry, calculus, and statistics homework questions with step-by-step explanations, just like a math tutor. Free trigonometric equation calculator - solve trigonometric equations step-by-step Compute answers using Wolfram's breakthrough technology & knowledgebase, relied on by millions of students & professionals. For math, science, nutrition, history ...Oct 3, 2016 · Multiply by 1 + cosx 1 + cosx to get. 1 − cos2x x(1 + cosx) = sin2x x(1 +cosx) = sinx ⋅ sinx x ⋅ 1 1 + cosx. Taking the limit as x → 0 gives. (0)(1)(1 2) = 0. Answer link. קוסינוס (מסומן ב- ) היא פונקציה טריגונומטרית בסיסית, המתאימה לכל זווית מספר ממשי בין (1-) ל-1. הרחבות שונות של הפונקציה משמשות במגוון תחומים, כגון: הגדרות שונות ב אנליזה (ובפרט ב אנליזה מרוכבת ...We would like to show you a description here but the site won’t allow us. May 29, 2023 · Misc 16 Find the derivative of the following functions (it is to be understood that a, b, c, d, p, q, r and s are fixed non-zero constants and m and n are integers ... Aug 20, 2015 · sec A = 1/cos A tan A = sin A/cos A sin^2 A + cos^2 A = 1 sec x + tan x = (1+sin x)/cos x = ((1+sin x)(1-sin x))/(cos x(1-sin x)) = (1-sin^2 x)/(cos x(1-sin x)) = cos ... Solution. Determine the formula of 1 - cos x sin x. It is known that 1 - c o s ( 2 θ) = 2 s i n 2 θ and s i n ( 2 θ) = 2 s i n θ c o s θ. So, 1 - cos x = 2 sin 2 x 2 and sin x = 2 sin x 2 cos x 2. Substitute the values into the expression 1 - cos x sin x and simplify: Hence, the formula for 1 - cos x sin x is tan x 2.Free math problem solver answers your algebra, geometry, trigonometry, calculus, and statistics homework questions with step-by-step explanations, just like a math tutor.Solve for x cos (x)=-1. cos (x) = −1 cos ( x) = - 1. Take the inverse cosine of both sides of the equation to extract x x from inside the cosine. x = arccos(−1) x = arccos ( - 1) Simplify the right side. Tap for more steps... x = π x = π. The cosine function is negative in the second and third quadrants. To find the second solution ... We would like to show you a description here but the site won’t allow us.Solve for x cos (x)=-1. cos (x) = −1 cos ( x) = - 1. Take the inverse cosine of both sides of the equation to extract x x from inside the cosine. x = arccos(−1) x = arccos ( - 1) Simplify the right side. Tap for more steps... x = π x = π. The cosine function is negative in the second and third quadrants. To find the second solution ...cos x = 1 / (sec x) Cosine Formulas Using Pythagorean Identity. One of the trigonometric identities talks about the relationship between sin and cos. It says, sin 2 x + cos 2 x = 1, for any x. We can solve this for cos x. Consider sin 2 x + cos 2 x = 1. Subtracting sin 2 x from both sides, cos 2 x = 1 - sin 2 x. Taking square root on both sides ....