Express cos(2x) in terms of sin(x).

Question

anonymous · Answer

This involves an trigonometric identity! Which one involves 2x?

anonymous · Answer

This is the double angle for cosine, but I don't know how to experss it in terms of sin(x).

anonymous · Answer

$\ \large \text{Okay, let's go back... What's the double angle identity for cosine?} $

anonymous · Answer

1-2sin^2(x) = cos(2x)

anonymous · Answer

$\ \Large \text{Exactly! That's it!  That's in terms of sin(x)!} $

anonymous · Answer

Oh! Okay :) Thanks. Do you mind helping me with another trig problem?

anonymous · Answer

$\ \Huge \text {I'll try my best ;)} $

anonymous · Answer

$\ \text {By the way -- Welcome to OpenStudy!} $

anonymous · Answer

Express |dw:1389147878332:dw| and find the sum of a+b+c= ? without using a calculator

anonymous · Answer

that's radical of a+b(radical c)

anonymous · Answer

and thanks :)

anonymous · Answer

Hmmm...I'm not really sure. I'd say start by knowing what cos60 is and working from there?

anonymous · Answer

Oh, alright thanks anyway :)

anonymous · Answer

1-2 sin^2 x

anonymous · Answer

we know that cos 2a =cos^2a-sin^2a =1-sin^2a-sin^2a=1-2sin^2a

anonymous · Answer

i think u got this