Question

Solve:-

The magnitude of addition of two vector is equal to magnitude of subtraction of two vector. Find angle b/w the vector.

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Answer 1

Refer the attachment...

Hope it helps you...

Answer 2

Magnitude of the sum of a and b is √(a²+b²+2(ab)cosX

Difference in their magnitudes is a-b

So,

√(a²+ b²+2(ab)cosX) = a-b

Squaring both sides,

a²+b²+2(ab) cosX = a²+ b²–2(ab)

2(ab)cosX+2(ab) = 0

2(ab)(cosX +1) = 0

Since 2(ab) cannot be zero, cos x+1=0

CosX=-1

X=180

Therefore, the angle between the vectors is 180°.