Asked by sumahr | 14th Jan, 2010, 08:11: PM

Expert Answer:

Let's denote the vector by bold face letters.

a + b + c = 0

-c = a + b

Using triangle law of vector addition,

c2 = a2+b2+2abcosθ,

where a, b and c are the magnitudes of the vectors and θ is the angle between the vectors added.

92 = 52+72+2x5x7xcosθ,

cosθ = 1/10

θ = cos-1(1/10)




Answered by  | 15th Jan, 2010, 09:38: AM

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