SOLUTION: prove each identity, SHOW WORK a. cos(2(3.14)-A)=cos A b. sin((3(3.14)/2)-A)=-cosA c. use the identity for sin(A+B) to prove the identity sin2A=2sinAcosA

Algebra ->  Trigonometry-basics -> SOLUTION: prove each identity, SHOW WORK a. cos(2(3.14)-A)=cos A b. sin((3(3.14)/2)-A)=-cosA c. use the identity for sin(A+B) to prove the identity sin2A=2sinAcosA       Log On


   

Question 199298This question is from textbook
: prove each identity, SHOW WORK
a. cos(2(3.14)-A)=cos A
b. sin((3(3.14)/2)-A)=-cosA
c. use the identity for sin(A+B) to prove the identity sin2A=2sinAcosA
This question is from textbook

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
I'll do the first one to get you started. Note: I'll use pi for 3.14


cos%282pi-A%29=cos%28A%29 Start with the given equation.


cos%282pi%29cos%28A%29%2Bsin%282pi%29sin%28A%29=cos%28A%29 Expand


%281%29cos%28A%29%2B%280%29sin%28A%29=cos%28A%29 Evaluate the cosine of 2pi to get 1. Evaluate the sine of 2pi to get 0


cos%28A%29%2B0=cos%28A%29 Multiply


cos%28A%29=cos%28A%29 Simplify


So this verifies the identity.