20sin^4 x power reduction

Step-by-step explanation:

20 sin^4x

=5 (4sin^4 x)

=5 (2sin²x) ²

=5 (1-cos 2x) ²

=5 (1-4cos2x+cos² (2x))

=5[1-4cos (2x) + {1+cos (4x) }/2]

=5/2[2-8cos (2x) + 1+cos (4x) ]

=5/2[3-8cos (2x) + cos (4x) ]