153k views
0 votes
Prove that 
cos 9x-cos 5x/sin17x-sin3x=-sin2x/cos10x

User Servn
by
8.4k points

1 Answer

2 votes
cos9x - cos5x = -2sin2x.sin7x
sin17x - sin3x = 2sin7x.cos10x
so f(x) =
(-2sin2x.sin7x)/(2sin7x.cos10x) =
(-sin2x)/(cos10x)

User Chis
by
8.8k points