SOLUTION: verify the identity. cos (x + pi/2) =

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Question 1089214: verify the identity.
cos (x + pi/2) = - sin x
Found 2 solutions by Theo, MathLover1:
Answer by Theo(13342) (Show Source):
You can put this solution on YOUR website!
this uses the basic trigonometric identity of:

cos(a + b) = cos(a) * cos(b) - sin(a) * sin(b).

replace a with x and b with pi/2 and you get:

cos(x + pi/2) = cos(x) * cos(pi/2) - sin(x) * sin(pi/2)

cos(pi/2) = 0

sin(pi/2) = 1

you can use your calculator to confirm.

equation bec0omes:

cos(x + pi/2) = cos(x) * 0 - sin(x) * 1

simplify to get:

cos(x + pi/2) = -sin(x)

QED (that's your solution).

Answer by MathLover1(20850) (Show Source):
You can put this solution on YOUR website!
verify the identity.

use Sum-Difference Formulas:
cos( � ) = �
in your case,
...........since and

SOLUTION: verify the identity. cos (x + pi/2) = - sin x