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Question:

If the magnitude of sum of two vectors is equal to the magnitude of difference of the two vectors, the angle between these vectors is: 0o, 45o, 90o, 180o

45o

0o

90o

180o

Solution:

Here, |A⃗+B⃗|=|A⃗−B⃗|
|A⃗+B⃗|²=|A⃗−B⃗|²
A²+B²+2A⃗.B⃗=A²+B²−2A⃗.B⃗
4A⃗.B⃗=0
As dot products of two vectors is zero so the angle between them will be 90o.