114 IN ENGLISH ► A(2; 4; 2), B(-4; 1; 2), C(O; 3; 8), D(2; -1; 6) and H(-1; 1; 5) are points in space. 1. Show that the points B, C and D define a plane. 2. a. Show that H lies in the plane (BCD). . Show that the line (AH) is orthogonal to the plane (BC 3. I is the midpoint of the segment [CD]. - Show that the lines (BI) and (CD) are perpendicula Find the area of the triangle BCD. Find the volume of the triangular pyramid ABCD. Merci infiniment pour votre aide.​