Rewrite the expression as the sine, cosine, or tangent of a double-angle. Then find the exact value of the trigonometric expression without the use of a calculator. cos sin Use the appropriate double-angle formula to rewrite the given expression as the sine, cosine, or tangent of the corresponding double-angle. cos sin (Do not evaluate. Use integers or fractions for any numbers in the expression. Type your answer in radians.) Find the exact value of the trigonometric expression without the use of a calculator. cos sin 3x (Use integers or fractions for any numbers in the expression. Type an exact answer, using radicals as needed.)