Question

Complete the identity sin(2θ) sin(4θ) cos(2θ) cos(4θ) = ?

Answer 1

Answer:

Step-by-step explanation:

Factor the left hand side as a difference of squares:

(

cos

2

θ

+

sin

2

θ

)

(

cos

2

θ

−

sin

2

θ

)

=

cos

2

θ

−

sin

2

θ

Apply the pythagorean identity  

cos

2

θ

+

sin

2

θ

=

1

:

1

(

cos

2

θ

−

sin

2

θ

)

=

cos

2

θ

−

sin

2

θ

cos

2

θ

−

sin

2

θ

=

cos

2

θ

−

sin

2

θ

L

H

S

=

R

H

S

Hopefully this helps!