Let the st. line a be the common section of the two planes α and β.Let the plane γ be perpendicular to a and intersects the planes α and β at the perpendicular st. lines m and n, i.e. the crosssection of γ and α is m, the crosssection of γ and β is n and m is perpendicular to n. The planes α and β are called perpendicular planes.
You need to install ActiveX plugin to be able to view this model.
You can download it here.
