H^2=\vec{h}\cdot\vec{h}=a^2+y^2b^2+z^2c^2+2(ayb+azc+ybzc)=\frac{a^2\left (1-\cos^2\alpha-\cos^2\beta-\cos^2\gamma+2\cos\alpha\cos\beta\cos\gamma\right )}{\sin^2\alpha}