Find the angle between ((5i + 3j)) and ((3i – 5j)).
-
A.
180° -
B.
90° -
C.
45° -
D.
0°
Correct Answer: Option B
Explanation
(a . b = |a||b|cos theta)
(cos theta = frac{a . b}{|a||b|})
= ( frac{(5i + 3j).(3i – 5j)}{(sqrt{5^2 + 3^2})(sqrt{3^{2} + (-5)^{2}})})
= (frac{0}{34} = 0)
(theta = cos^{-1} 0 = 90°)