№1.18. Given the vector. It is necessary: ​​a) to calculate the mixed product of the three vectors; b) find the module of the vector product; c) calculate the scalar product of two vectors; d) check whether the two vectors are collinear or orthogonal; e) check whether the three vectors are coplanar: a (9; -3; 1); b (3; -15; 21); c (1; -5; 7).
№ 2.18. The vertices of the pyramid are at points A (5; –4; 4); B (–4; –6; 5); C (3; 2; –7); D (6; 2; –9) .........
No. 3.18. Three forces P are given (–5; 8; 4); Q (6; –7; 3); R (3; 1; –5); attached to point A (2; –4; 7). Calculate a) the work produced by the resultant of these forces; when the point of its application, moving straight, moves to point B (0; 7; 4); b) size
the moment of the resultant of these forces relative to point B.