SOLUTION: My homework tells me to prove an identity, sin(x-3 times pie divided by 2)=cosx I cant figure it out please help

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Question 88275: My homework tells me to prove an identity, sin(x-3 times pie divided by 2)=cosx
I cant figure it out please help
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
sin%28x-3%2Api%2F2%29=cos%28x%29



sin%28x%29cos%283pi%2F2%29-cos%28x%29sin%283pi%2F2%29=cos%28x%29 Use the trig identity sin%28A-B%29=sin%28A%29cos%28B%29-cos%28A%29sin%28B%29

sin%28x%29cos%283pi%2F2%29-cos%28x%29%28-1%29=cos%28x%29 Evaluate sin%283pi%2F2%29 to get -1


sin%28x%29%280%29-cos%28x%29%28-1%29=cos%28x%29 Evaluate cos%283pi%2F2%29 to get 0


cos%28x%29=cos%28x%29 Multiply. So the identity has been proven

As always we can graph the two expressions (the given and the result) to see if they are equivalent.