Question

Question #6fd1b

Answer 1

`LHS=cos(tan^-1v)`

`=cos(sec^-1sqrt(1+v^2))`

`=cos(cos^-1(1/sqrt(1+v^2)))`

`=1/sqrt(1+v^2)=RHS`

Alternative

Let `tan^-1v=x=>v=tanx`

So `LHS=cos(tan^-1v)`

`=cosx=1/secx=1/sqrt(1+tan^2x)=1/sqrt(1+v^2)=RHS`