How do you calculate the angle between two vectors?

The formula axb = |a||b|sinθ is given in the formula bookletTherefore, θ, the angle between both vectors a and b is equal to sin^-1 ((axb)/(|a||b|))Remember, axb can be found by multiplying a and b together as matrices (if a reminder is needed on how to do this, I'll show you on a whiteboard); and |a| can be found by square rooting all the components of a squared (e.g. square root of a_i²+ a_j² + a_k² if the vector is three dimentional).