SOLUTION: prove or disprove without a calculator. 1. sin(pi/2 + theta) = cos theta

Algebra ->  Trigonometry-basics -> SOLUTION: prove or disprove without a calculator. 1. sin(pi/2 + theta) = cos theta       Log On


   

Question 139726: prove or disprove without a calculator.
1. sin(pi/2 + theta) = cos theta
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!
Can't render theta on this site, so I'll use something else
sin%28alpha%2Bbeta%29=sin%28alpha%29cos%28beta%29%2Bcos%28alpha%29sin%28beta%29

So
sin%28pi%2F2%2Bx%29=sin%28pi%2F2%29cos%28x%29%2Bcos%28pi%2F2%29sin%28x%29, but sin%28pi%2F2%29=1 and cos%28pi%2F2%29=0, so


sin%28pi%2F2%2Bx%29=1%2Acos%28x%29%2B0%2Asin%28x%29=cos%28x%29