Question

giúp vs

Answer 1

Với `1+cos 2\alpha ne 0; tan \alpha ne 0` có:

 `VT=[sin 2\alpha]/[1+cos 2\alpha]`

     `=[2sin \alpha .cos \alpha]/[1+2cos^2 \alpha -1]`

    `=[sin \alpha]/[cos \alpha]=tan \alpha = VP`

 `=>đpcm`.