(Problem 3:) Consider a tetrahedron formed by four triangles (Fig. 1). Show that the area of the triangle (5;) formed by the projection in the x;-direction (e.g., d; is the area on the za-z3 plane) is 5Sj = ('I'L ) 6j)55 where 45 is the area of a triangle oblique to the xy, x5, and z3 axes. Fig.1