Finding the Angle Between Two Vectors A & B

[vipertongn]

Homework Statement

Two vectors are given by A = -2 i + 5 j and B = 2 i + 3 j
Also find the angle between them

Homework Equations

Not really sure but from my book i get A x B = -B x A

The Attempt at a Solution

the answer is -16, but I'm confused I thought that it should look like -6 + 10 but why is it minus ten?

How would I use this to find the angle?

 

[Ofey]

Do you know how to set up a determinant for vector product? From the determinant you can easilly calculate the product vector. Remember the result of a vector product is always a vector.

When you know the vector product you can find the angle from

(AxB)=|A||B|sin(A,B)

Where A and B are the 2 vectors, (AxB) is the vector product and |A|/|B| are the lenghts of the vectors.