Trig Identities Help

[g0dsend]

I really don't think I understand how to do any of this because I keep getting answer that aren't in the answer bank,, but I am focusing on number 7 right now.

here is my work:

I've been trying to do these for hours.

 

[Deleted member 4993]

I really don't think I understand how to do any of this because I keep getting answer that aren't in the answer bank,, but I am focusing on number 7 right now.

here is my work:

I've been trying to do these for hours.

Hint: For # 7

1 - cos²(Θ) = sin²(Θ)

and

(a+b)(a-b) = a² - b²