Question

Please help! When evaluating sin(2Cos^-1(4/5)) what is an identity used in the solution?
a. cos2x = 1 - 2cos^2x
b. cos2x = sin^2x - cos^2x
c. sin2x = 1 - 2sin^2x
d. sin2x = 2sin x cos x

Answer 1

\[\sin(2\cos ^{-1}4/5)\] is that the right equation?

Answer 2

Yes

Answer 3

http://www.wolframalpha.com/input/?i=sin%282cos%5E-1%284%2F5%29%29
or
http://www.mathway.com/problem.aspx?p=precalculus?p=sin(2cosSMB07-1(4SMB105))?p=FindSMB15theSMB15ExactSMB15Value

maybe they will help

Answer 4

I can't view the steps :( You wouldn't know the answer?

Answer 5

@SantanaG