Question

Prove that Cos^4 A + 2 cos^2 A [1 - 1 /sec^2A] = (1-sec^4 A) ​

Answer 1

Step-by-step explanation:

cos

2

A=cos

4

A−sin

4

A

RHS

cos

4

A−sin

4

A

=(cos

2

A−sin

2

A)(cos

2

A+sin

2

A)

=(cos

2

A)(1)

=cos

2

A (proved)

Hence LHS=RHS