Prove the following trigonometric identities:
11+sin A+11−sin A=2 sec2 A
LHS = 11+sinA11+sinA + 11–sinA11–sinA
We know that cos2θ+sin2θ=1
sec θ=1cos θ
LHS=11+sin A+11−sin A
=1+sin A+1−sin A(1+sin A)(1−sin A)
=21−sin2 A
=2cos2 A
=2sec2 A=RHS