SOLUTION: Prove that sin(90-A)=cosA

Algebra ->  Trigonometry-basics -> SOLUTION: Prove that sin(90-A)=cosA      Log On


   

Question 1040634: Prove that
sin(90-A)=cosA
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Use the formula,
sin%28X-Y%29=sin%28X%29cos%28Y%29-cos%28X%29sin%28Y%29
Substituting,
sin%2890-A%29=sin%2890%29cos%28A%29-cos%2890%29sin%28A%29
sin%2890-A%29=1%2Acos%28A%29-0%2Asin%28A%29
sin%2890-A%29=cos%28A%29