Show that the vectors 5a + 6b + 7c, 7a - 8b + 9c, 3a + 20b + 5c are coplanar. Where a, c, and c are non-coplanar.

Prove that the four points 2a + 3b - c, a - 2b + 3c, 3a + 4b -2c and a - 6b + 6c are coplanar, where a, b, c are no-coplanar Prove t...

If a and b are unit vectors and θ is the angle between them, then how do I prove that sin θ/2 = ½ |a-b|?

Prove that the three points -2a + 3b + 5c, a + 2b + 3c and 7a - c are colinear, where a, b, c are non-coplanar.

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