SOLUTION: Use the Angle sum identity to verify: sin(x+(pi/2))=cos x

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Question 1036926: Use the Angle sum identity to verify:
sin(x+(pi/2))=cos x
Answer by ikleyn(52784) About Me  (Show Source):
You can put this solution on YOUR website!
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Use the Angle sum identity to verify:
sin(x+(pi/2))=cos x
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

the Angle sum identity for sine is

sin%28alpha%2Bbeta%29 = sin%28alpha%29%2Acos%28beta%29+%2B+cos%28alpha%29%2Asin%28beta%29

(see, for example, the lesson Addition and subtraction formulas in this site).


Now apply it:

sin%28x%2B%28pi%2F2%29%29 = sin%28x%29%2Acos%28pi%2F2%29+%2B+cos%28x%29%2Asin%28pi%2F2%29.


Remind that  cos%28pi%2F2%29 = 0  and  sin%28pi%2F2%29 = 1. Then you can continue the line above as

= sin(x)*0 + cos(x)*1 = cos(x).

Verified.