Question

slove sin7θ+sin4θ+sinθ=0​

Answer 1

sin 7@+sin4@+sin@=0

using formula

sin A+sin B=2sin A+B/2*cos A-B/2

sin4@+2sin4@cos3@=0

sin4@(1+2cos3@)=0

sin4@=0

4@=nπ

@=nπ\4

2cos3@= -1

cos3@=-1/2

@=-nπ\18