Question

How do you verify `1 + cos 2a = 2/(1+ tan^2a)`?

Answer 1

LHS
`=1+cos2alpha`
`=1+(1-tan^2alpha)/(1+tan^2alpha)`
`=(1+canceltan^2alpha+1-canceltan^2alpha)/(1+tan^2alpha)`
`=2/(1+tan^2alpha)`=RHS