9.4 Exercise 57

Algebraically determine whether each of the given equation is an identity. If it is not an identity, replace the right-hand side with an expression equivalent to the left side. Verify the results by graphing both expressions on a calculator.

$\frac{\cos \left(10 \theta\right) + \cos \left(6 \theta\right)}{\cos \left(6 \theta\right) - \cos \left(10 \theta\right)} = \cot \left(2 \theta\right) \cot \left(8 \theta\right)$