If a and b are two unit vectors and a+b is also a unit vector then what is the angle between a and b

Asked by  | 18th Mar, 2008, 12:00: PM

Expert Answer:

Hi Aparna,

You can answer this question in the following way:

Let the angle between the vectors be Φ

Thus we have the following relation:

 |a+b|2 = |a|2 + |b|2 +2|a||b|cosΦ

As a and b and a+b are unit vectors |a|, |b|, |a+b| are 1

Thus solving we get: cosΦ = -0.5

Thus Φ=120o

Topper Learning Team

Answered by  | 12th Jun, 2008, 02:13: PM

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