Precal trig identities help!?

Question

verify the following equations please.. 

1. cos(x+y)/cosxsiny=coty-tanx 

2. (sin^2x-cos^2x)/(1-cot^2x)=sin^2x 

3. sin4x=2sin2xcos2x

Answer 1

1)

Left hand side identity

Apply the formula

Recall and

= Right hand side identity

 

2)

Left hand side identity

= Right hand side identity

 

3)

Left hand side identity

Apply double angle formula

= Right hand side identity