How do you compute the angle between two vectors?

Question

Compute the angle, in radians, between the two vectors:

A = -4i^ + 5j^
B = 2i^ + 3j^

Just for clarification, the ^ should be ABOVE the i or j, but I can't get it to come out correctly.

Thanks!

Answer 1

Best Answer - Chosen by Voters

You can use the dot product.
First find the magnitude of A and B
|A| = sqrt (4^2 + 5^2) = 6.40
|B| = sqrt (2^2 + 3^2) = 3.61
Now find the | A xB| = |-8 +15| = 7
cos y = |Ax B|/ |A||B| = 7/23.1 = 0.303
y = 72.4 degrees, this is the angle between the vectors