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If x=i3j and y=6i+j, calculate the angle be...

If x=i3j and y=6i+j, calculate the angle between x and y

A.

trong>

B.

75°

C.

81°

D.

85°

Correct answer is C

x.y=|x||y|cosθ

x.y=(i3j).(6i+j)=63=3

|x|=12+(3)2=10

|y|=62+12=37

\cos\theta = \frac{3}{\sqrt{370}} = 0.1559

\theta = \cos^{-1} 0.1559 \approxeq 81°