Solve the Problem $$\tan ^ { 2 } \mathrm { u } ( 1 + \cos ( 2 \mathrm { u } ) ) = 1 - \cos ( 2 \mathrm { u } )$$

Essay

Solve the problem.

- $$\tan ^ { 2 } \mathrm { u } ( 1 + \cos ( 2 \mathrm { u } ) ) = 1 - \cos ( 2 \mathrm { u } )$$