Question

Show that the equation is not an identity by finding a value of x for which both sides are defined but not equal. cos x - cos x sinx = cos^3 x

A. π

B. 0

C. (pi)/4

D. (pi)/2

Answer 1

i think its x = pi/4
lets check
cos x - cosx sinx = 1/sqrt 2 - 1/2 = 0.207

cos^3 x = (1/sqrt2)^3 = 1 / 2^(3/2) = 0.3535

thats the one

C

Answer 2

thnx!