■ Algorithms Dealing with Angles

If we set = − = −andu a b v c b, then the cosine of the bond angle will be given by

( ) ( )θ = − − − −

cos . Ta b c b

a b c b (4.2)

Once this quantity is calculated, the required bond angle can be easily derived by taking the inverse cosine of the quantity on right-hand side of the last equation.