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Find the angle between i + 5j and 5i - J
...

Find the angle between i + 5j and 5i - J

A.

0 $^o$

B.

45 $^o$

C.

60 $^o$

D.

90 $^o$

View answer & explanation

Correct answer is D

a = i + 5j and b = 5i - j

cos $\theta$ = $\frac{a.b}{|a|.|b|}$

= $\frac{(1 \times 5) + (5x - 1)}{(\sqrt{1^2 + 5^2}) (5^2 + (-1))^2}$

= $\frac{5 - 5}{\sqrt{26}\times \sqrt{26}}$ = 0

x = cos $^{-1}$ (0), x = 90 $^o$

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