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Find the angle between (5i+3j) and (3i5j)...

Find the angle between (5i+3j) and (3i5j)

A.

180°

B.

90°

C.

45°

D.

Correct answer is B

a.b=|a||b|cosθ

cosθ=a.b|a||b|

= (5i+3j).(3i5j)(52+32)(32+(5)2)

= 034=0

\theta = \cos^{-1} 0 = 90°