Dihedral angle solution method

1, the definition of the method (respectively, to the intersection of the line as a plumb line, the angle between the two lines) 2, three plumb line method: over a half of the plane to the other half of the plane and the intersection of the line as a plumb line to make a projectile by the tan angle solution, which COS dihedral angle = projectile area / original area. 3, plumb line method: to find out the plumb line of the intersection of the plumb line and make the plumb line with the intersection of half-planes, to ask for the angle. 4, the vector method ① first to establish a right-angle coordinate system, and find the coordinates of each point, and then the coordinates of each point. Find the coordinates of the points. ② set the surface S1 normal vector and surface S2 normal vector. Then find the cosine of the angle θ of the sum. (iv) Observe the direction of the sum from the image. If one of the two normal vectors points to the interior of the dihedral angle and the other points to the exterior of the dihedral angle, then the magnitude of the dihedral angle is θ. If the two normal vectors point to the interior or exterior of the dihedral angle at the same time, then the magnitude of the dihedral angle is π - θ. Specific topics need to be analyzed in detail.