Question

If a=4i+6j-3k and b=-2i-5j+7k, find the angle between the vectors a and b

Answer 1

Let the required angle be θ.

We know,

A.B = AB cosθ - - - - - - - - - - - - - - 1

=> θ = cos^-1 x [A.B/(AB)]

Now,

A.B= -8 - 30 - 21 = -59 By 1

A = (42 + 62 + 32)1/2 = 7.8

B = (22 + 52 +72)1/2 = 8.8

So. AB = 68.7 (approx)

Thus,

θ = cos^-1 x (-59/68.7) = 150

Answer 2

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