What is the angle between (a = (3i – 4j)) and (b = (6i + 4j))?
-
A.
13° -
B.
87° -
C.
100° -
D.
110°
Explanation
(a . b = |a||b| cos theta)
(a = 3i – 4j; b = 6i + 4j)
(18 – 16 = (sqrt{3^{2} + (-4)^{2}})(sqrt{6^{2} + 4^{2}}) cos theta)
(2 = 5sqrt{52} cos theta)
(cos theta = frac{2}{5sqrt{52}} = 0.0555)
(theta = 86.8° approxeq 87°)