Question

write in terms of sine only : 5(sin2x-cos2x)

Answer 1

Trig identity!

Answer 2

not very helpful

Answer 3

Let me look it up on Google.

Answer 4

http://www.sosmath.com/trig/Trig5/trig5/trig5.html

Answer 5

A pair of commonly memorized trig identities are
sin(2x) = 2sinxcosx
cos(2x) = 1 - 2sin^2(x)

One of them might be useful

Answer 6

Do you know substitution by equality?

Answer 7

yeah of course

Answer 8

but what are we substituting ?

Answer 9

Your question asks for everything in terms of sine right?

Answer 10

So substitute everything that has cosine by something that has sine but that are of course equal as well.

Answer 11

ok but 2sinxcosx is one term

Answer 12

You should not substitute that ones once it will still give you a cosine.