Question

prove that (1/seca-1)-(1/seca+1)=2 cot^2a

Answer 1

$\frac{1}{seca - 1} - \frac{1}{seca + 1} \\ \\ = \frac{seca + 1 - seca + 1}{ {sec}^{2}a - 1 } \\ \\ = \frac{2}{ {tan}^{2} a} \\ \\ = 2 {cot}^{2} a$