Question

c) Solve : sinx + sin3x + sin5x = 0.
(3)​

Answer 1

Answer:

Sinx+sin3x+sin5x=0

{Sinx+sin5x}+sin3x=0

2sin(x+5x)/2.cos(x-5x)/2+sin3x=0

2sin3x.cos2x+sin3x=0

Sin3x(2cos2x+1)=0

Hence

Sin3x=0 2cos2x+1=0

X=0 cos2x=-1/2

Cos2x=-cos60

Cos2x=cos(180-60)

Cos2x=cos120

2x=120

X=60