How do you find the exact value of cos (pi)/2? Trigonometry Right Triangles Trigonometric Functions of Any Angle 1 Answer Alan P. Sep 7, 2015 #cos(pi/2) = 0# #cos(pi)/2 = -1/2# #color(white)("XXXXXXXXXXXXX")#it depends on which you meant Explanation: (see diagram below) Answer link Related questions How do you find the trigonometric functions of any angle? What is the reference angle? How do you use the ordered pairs on a unit circle to evaluate a trigonometric function of any angle? What is the reference angle for #140^\circ#? How do you find the value of #cot 300^@#? What is the value of #sin -45^@#? How do you find the trigonometric functions of values that are greater than #360^@#? How do you use the reference angles to find #sin210cos330-tan 135#? How do you know if #sin 30 = sin 150#? How do you show that #(costheta)(sectheta) = 1# if #theta=pi/4#? See all questions in Trigonometric Functions of Any Angle Impact of this question 3465 views around the world You can reuse this answer Creative Commons License