f Now solve the equation cos x sin x 1 for cos x and substitute this into your answer to part d above Simplify You should now have a formula for cos 2x in terms of just sin x g In summary write the 3 formulas you ve derived cos 2x cos 2x cos 2x Choose to either memorize or derive these formulas as needed 2 Find each by using a double angle formula derived above Don t use a calculator a cos 75 b sin 75 bu corine and simplifying