Question

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

Answer 1

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

Answer 2

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

Answer 3

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

Answer 4

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

Answer 5

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

Answer 6

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

Answer 7

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

Answer 8

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

Answer 9

Express and find the sum of a+b+c= ? without using a calculator

Answer 10

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

Answer 11

and thanks :)

Answer 12

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

Answer 13

Oh, alright thanks anyway :)

Answer 14

1-2 sin^2 x

Answer 15

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

Answer 16

i think u got this