SOLUTION: How do I simplify {{{cos(2x-pi/2)}}} using sum and difference identities?

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Question 1107872: How do I simplify cos%282x-pi%2F2%29 using sum and difference identities?
Answer by ikleyn(52786) About Me  (Show Source):
You can put this solution on YOUR website!
.
First step is  TO LEARN  sum and difference identities.


See the lessons

    - FORMULAS FOR TRIGONOMETRIC FUNCTIONS

    - Addition and subtraction formulas

    - Addition and subtraction formulas - Examples


in this site.


Second step is to learn on how to apply them.


    a)  cos%282x-pi%2F2%29 = cos%282x%29%2Acos%28pi%2F2%29+%2B+sin%282x%29%2Asin%28pi%2F2%29 = cos(2x)*0 + sin(2x)*1 = sin(2x);


    b)  sin(2x) = sin(x+x) = sin(x)*cos(x) + cos(x)*sin(x) = 2*sin(x)*cos(x).


Answer.  cos%282x-pi%2F2%29 = 2*sin(x)*cos(x).

That's all.