Question

I need to write this as sine cosine or tangent
sin 9x cos x - cos 9x sin x

Answer 1

Do I work backwards so Sin(a+b) where a = 9x and b = x?

Answer 2

Sin10x

Answer 3

no

Answer 4

Why not?

Answer 5

cos it doesnt work like that without an equation

Answer 6

sin 9x cos x - cos 9x sin x

sin(a + b) = sin(a)cos(b) + cos(a)sin(b)

Answer 7

So then its sin8x

Answer 8

sin(a-b) = sin(a)cos(b ) - cos(a)sin(b)
comparing to the above question,
sin 9x cos x - cos 9x sin x =sin(9x-x)=
=sin(8x)

Answer 9

Ok