I'm completely stumped. were supposed to prove the equations true. if you could help me that would be great!

3.) sec^2(θ)-sec^2(θ)sin^2(θ)=1

4.) sec^2(θ)cot^2(θ)-1=cot^2(θ)

5.) 1/sec(θ)-cos(θ)=cot(θ)csc(θ)

6.) sec^2(θ)+csc^2(θ)=csc^2(θ)sec^2(θ)

7.) [1/sin(θ)+1] - [1/sin(θ)-1]=2sec^2(θ)

8.) [sin(θ)tan(θ]/[1-cos(θ)]=sec(θ)=1