Trigonometric Value from the Angle Between Two Vectors

Let $\theta$ be the angle between the vectors $\vec{a} = 2\hat{i} + 3\hat{j}$ and $\vec{b} = -3\hat{i} + 4\hat{j}$. Find the value of $\sin 2\theta$. The answer is in the form $\frac{\alpha}{\beta}$ where $\alpha$ and $\beta$ are coprime integers. Input the value of $\alpha+\beta$.