CUET Preparation Today
If $cos^{-1}\alpha + cos^{-1}\beta +cos^{-1}\gamma = 3\pi , $ then $\alpha ( \beta + \gamma ) + \beta (\gamma +\alpha ) + \gamma ( \alpha + \beta )$ equals : |
0 1 6 12 |
6 |
The correct answer is option (3) → 6 $\cos^{-1}\alpha + \cos^{-1}\beta +\cos^{-1}\gamma = 3\pi$ ⇒ iff $α=β=γ=-1$ so $α(β+γ)+β(γ+α)+γ(α+β)$ $=2+2+2=6$ |
