Question

Please help me. I can't seem to get the answer of 165 degrees.

Find the angle ϴ between the vectors.
u=3i-3j, v=-2i+2√3j

Answer 1

The magnitude of u is sqrt 18.
The magnitude of v is 4
The dot product of u and v is
u*v = -6 -6sqrt3
= -6(1+sqrt3)
The cosine of the angle between the vectors is
(u*v)/|u||v|