Assignment No 8 (3-D Geometry)
Assignment No 8 (3-D Geometry)
Assignment No 8 (3-D Geometry)
1. For each of the following vectors, find its length and find a vector of length one (unit" vector)
parallel to it.
a = (4;-4; 2); b = (2; 1; 0) ; c = (4; 0; 1;-2; 0)
3.A triangle has vertices A,B and C which have co-ordinate vectors (4; 1; 7); (7;-4; 6) and (6; 2; 8)
respectively. Find the lengths of the sides of the triangle and deduce that the triangle is right-angled.
4. A cube has vertices at the 8 points O (0; 0; 0), A(1; 0; 0), B (1; 1; 0), C (0; 1; 0), D(0; 0; 1),
E (1; 0; 1), F (1; 1; 1), G(0; 1; 1). Sketch the cube, and then find the angle between the diagonals
OF and AG .
5. Find the areas of, and the normals to the planes of, the following parallelograms:
(a) the parallelogram spanned by (1; 3; 2) and (0; 2; 4);
(b) a parallelogram which has vertices at the three points A(0; 2; 1), B(-1; 3; 0) and C(3; 1; 2).
7. A tetrahedron has vertices A, B, C and D with coordinate vectors for the points being a =(0; 1; 2),
b = (-1; 4; 1), c = (1; 0; 3) and d = (-3; 1; 2). Find parametric vector equations for the two altitudes
of the tetrahedron which pass through the vertices A and B, and determine whether the two altitudes
intersect or not.
Note: An altitude of a tetrahedron through a vertex is a line through the vertex and perpendicular to
the opposite face.
9. Find parametric vector, point-normal, and Cartesian forms for the following planes:
(a) the plane through (1; 2;-2) perpendicular to (-1; 1; 2);
(b) the plane through (1; 2;-2) parallel to (-1; 1; 2) and (2; 3; 1);
(d) the plane through the three points (1; 2;-2), (-1; 1; 2) and (2; 3; 1);
(d) the plane with intercepts -1, 2 and -4 on the x , y and z axes;
10.
(a) Find the plane through (1; 2;-2) which is parallel to (-1; 2;-2)
(b) Find the line of intersection of the planes x .(1; 2; 3) = 0 and x = λ 1 (2,1,2) + λ 2 (1,0,1)
14. Four points have coordinate vectors A(1; 0; 2), B(-1; 2; 3), C(0; 1; 1) and D(2; 0;-1).
(a) Find the parametric vector equations of the line through A and B and the line through C and D.
(b) Find the shortest distance between the lines AB and CD.
(c) Find the point P on AB and point Q on CD such that PQ is the shortest distance between the
lines AB and CD.