Q: If the line x = y = z intersect the line x sin A + y sin B + z sin C = 2d2, x sin 2A + y sin 2B + z sin 2C = d2 then $sin\frac{A}{2} sin\frac{B}{2} sin\frac{C}{2}$ is equal to (where A + B + C = π)
(A) $\frac{1}{16}$
(B) $\frac{1}{8}$
(C) $\frac{1}{32}$
(D) $\frac{1}{12}$
Sol. Let (λ, λ, λ) be the point of intersection of two lines.
⇒ λ(sin A + sin B + sin C) = 2d2 and λ(sin 2A + sin 2B + sin 2C) = d2
$\large \frac{sin 2A + sin 2B + sin 2C}{sin A + sin B + sin C} = \frac{1}{2}$
$\large sin\frac{A}{2} sin\frac{B}{2} sin\frac{C}{2} = \frac{1}{16} $