Question

Question #4d1cc

Answer 1

Develop the left side:
`LS = cos u/(1 - sin u/(cos u)) + sin u/(1 - cos u/(sin u)) =`
`= cos^2 u/(cos u - sin u) - sin^2 u/(cos u - sin u) =`
`= (cos^2 u - sin^2 u)/(cos u - sin u) =`
`= [(cos u - sin u)(cos u + sin u)]/(cos u - sin u) = cos u + sin u`#