which of relations in true?

Question

Cos a=p Cot a= q which one is true....

1) 1/p^2+1/q^2=1

2) 1/p^2-1/q^2=1

3) 1/p^2+1/q^2=0

4) 1/p^2-1/q^2=0

Answer 1

Investigate the identity

1 + tan² a = sec² a