Question

Find the value of
2 cos x - cos 3x- cos 5x =​

Answer 1

Answer:

f(x)=2cosx−cos3x−cos5x

=2cosx−(2cos4xcosx)

=2cosx(1−cos4x)

=2cosx[cos

2

2x+sin

2

2x−(cos

2

2x−sin

2

2x)]

=2cosx×2sin

2

2x[cos2x=cos

2

x−sin

2

x]

=4cosxsin

2

2x

=4cosx(2sinxcosx)

2

⇒f(x)=16sin

2

xcos

3

x

Answer 2

Answer:

2cos x - cos3x - cos5x = 16 sin^2 x cos ^3 x