Three Dimensional Geometry

Let $\pi_1$ be the plane determined by the vectors $\hat{\mathbf{i}}+2 \hat{\mathbf{j}}$ and $3 \hat{\mathbf{j}}-2 \hat{\mathbf{k}}$. Let $\pi_2$ be the plane determined by the vectors $\hat{\mathbf{j}}+2 \hat{\mathbf{k}}$ and $3 \hat{\mathbf{k}}-2 \hat{\mathbf{i}}$. If $\theta$ is the angle between $\pi_1$ and $\pi_2$, then $\cos \theta=$