5. New challenge: Start with 1 + tan20 . Use the basic Pythagorean identity and, make a substitution for sin 0 so you can rewrite the expression as an expression involving only cos 0. What restriction would you have to have on the domain? 6. Use algebra to untangle the following expression and rewrite it as a much simpler expression involving only cos 0. This will take several steps. (tan20) ( 1 1 + -cos 0 1+cos 0