Answer:
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)]
