Question

If a and b are two unit vectors and
→
R = a + b and if|RI=R, then (a)R<0 b)R>2 c) 0≤R≤2 d) R must be 2
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Answer 1

Answer:

Option D

Explanation:

We know that:

R = root[A^2+B^2+2ABcos(angle between vectors)]

But It is given that

R = A+B

Means that cos(angle) = 0 degree ----- ( Proove it urself)

This Implies that A and B are parallel and parallel vectors have same direction.

Now it is given that A and B are unit vectors

So R = 1+1

Hence R = 2