Question

This is the question​

Answer 1

let me take teta=A ( cos^2(90-A) =Sin^2 A)

sec^2 A- cot^2(90-A)= sin^2 A +cos^2 A

1/cos^2 A - sin^2 A/cos^2A =1

1-sin^2A/cos^2A=1

1-sin^2 A= cos^2 A

sin^2 A+ cos ^2 A =1

1=1

hence proved

Hope it helps you