Question

Assertion (A) : For two non-zero vectors a→ and b→, a→ · b→ = b→ · a→. Reason (R) : For two non-zero vectors a→ and b→, a→ × b→ = b→ × a→.

The position vectors of vertices of △ ABC are A(2î – ĵ + k̂), B(î – 3ĵ – 5k̂) and C(3î – 4ĵ – 4k̂). Find all the angles of △ ABC.

If →a and →b are two vectors such that |→a| = 1, |→b| = 2 and →a · →b = √3, then the angle between 2→a and –→b is:

An instructor at the astronomical centre shows three among the brightest stars in a particular constellation. Assume that the telescope is located at O(0, 0, 0) and the three stars have their locations at the points D, A and V having position vectors 2î + 3ĵ + 4k̂, 7î + 5ĵ + 8k̂ and –3î + 7ĵ + 11k̂ respectively.