14. Angles Between Vectors

The scalar is the length of the vector

Say

Law of Cosines

Where:

• , and : lengths of the sides of a triangle
• : angle opposite the side

So, if is a scalar multiple of () where , then

And, if is a scalar multiple of () where , then

and are perpendicular if the angle between them is

If and are perpendicular, then

If and are non-zer0 and , then they are perpendicular

If then and are orthogonal.