Question

Is the magnitude cef (A+B)
as that magnitude of (B+A) a​

Answer 1

Answer: Let x be angle between vectors A and B

|A+B| = √(|A|²+|B|²+2|A|*|B|*cos(x))

Since |A+B|=|A|=|B|

|A+B|²=|A|²+|A|²+2*|A|*|A|*cos(x)

implies |A|²=|A|²+|A|²+2*|A|*|A|*cos(x)

implies |A|²+2*|A|*|A|*cos(x) = 0

implies |A| = 0 or cos(x) = -1/2

implies x=120 degree (since angle between two zero vectors is indeterminate)