Đáp án `+` Giải thích các bước giải:

Có:

`VP = sin alpha cos alpha (1 + tan alpha )(1 + cot alpha )`

`     = (cos alpha + tan alpha . cos alpha )(sin alpha + cot alpha . sin alpha )`

`     = (cos alpha + (sin alpha)/(cos alpha) . cos alpha )(sin alpha + (cos alpha)/( sin alpha ) . sin alpha )`

`     = (cos alpha + sin alpha)(sin alpha + cos alpha )`

`     = sin^2 alpha + cos^2 alpha + 2sin alpha cos alpha`

`     = 1 + 2 sin alpha cos alpha`

`     = VT`

`=> d c c m`

        $\color{#FFB6C1}{♡}\quad\color{#D8BFD8}{T}\color{#E6CCE6}{r}\color{#DDA0DD}{a}\color{#BA55D3}{n}\color{#9370DB}{g}\quad\color{#FFB6C1}{♡}$