Angle between two planes == = angle between normals. Distance of point (x0,y0,z0)(x_0, y_0, z_0)(x0,y0,z0) from ax+by+cz+d=0ax + by + cz + d = 0ax+by+cz+d=0: ∣ax0+by0+cz0+d∣a2+b2+c2\dfrac{|ax_0 + by_0 + cz_0 + d|}{\sqrt{a^2 + b^2 + c^2}}a2+b2+c2∣ax0+by0+cz0+d∣.