№1 Given four points A1 (2; 3; 5); A2 (5; 3; –7); A3 (1; 2; 7); A4 (4; 2; 0). Draw up the equations: a) plane A1A2A3; b) straight line A1A2; c) direct A4M; perpendicular to the plane A1A2A3; d) line A3N parallel to line A1A2; e) a plane passing through point A4; perpendicular to the straight line A1A2. Calculate: e) the sine of the angle between the straight line A1A4 and the plane A1A2A3; g) the cosine of the angle between the Ohu coordinate plane and the A1A2A3 plane.

№2 Find the projection of the point M (4; –3; 1) on the plane x - 2y - z - 15 = 0.

№3 Make an equation for the plane passing through the point K (2; - 5; 3) parallel to the Oxz plane.