Question

Verify sin4x - sin2x = cos4x-cos2x

Answer 1

sin⁴x - sin²x = cos⁴x - cos²x

Solve the right hand side of the equation

That's

sin⁴x - sin²x

From trigonometric identities

sin²x = 1 - cos²x

So we have

sin⁴x - ( 1 - cos²x)

sin⁴x - 1 + cos²x

sin⁴x = ( sin²x)(sin²x)

That is

( sin²x)(sin²x)

So we have

( 1 - cos²x)(1 - cos²x) - 1 + cos²x

Expand

1 - cos²x - cos²x + cos⁴x - 1 + cos²x

1 - 2cos²x + cos⁴x - 1 + cos²x

Group like terms

That's

cos⁴x - 2cos²x + cos²x + 1 - 1

Simplify

We have the final answer as

cos⁴x - cos²x

So we have

cos⁴x - cos²x = cos⁴x - cos²x

Since the right hand side is equal to the left hand side the identity is true

Hope this helps you