Let chord PQ of length 3 √ 13 of the parabola y^2=12 x be such that the ordinates of points P and Q are in the ratio 1: 2. If the chord PQ subtends…

Let chord PQ of length $\displaystyle 3 \sqrt{13}$ of the parabola $\displaystyle y^2=12 x$ be such that the ordinates of points P and Q are in the ratio $\displaystyle 1: 2$. If the chord PQ subtends an angle $\displaystyle \alpha$ at the focus of the parabola, then $\displaystyle \sin \alpha$ is equal to: