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.
2cos² (-22.5 °)-1
Use the appropriate double-angle formula to rewrite the given expression as the sine, cosine, or tangent of the corresponding double-angle.
2cos² (-22.5 °)-1= _____
(Do not evaluate. Type your answer in degrees. Do not include the degree symbol in your answer)
Find the exact value of the trigonometric expression without the use of a calculator.
2cos²(-22.5 °)-1= _____
(Use integers or fractions for any numbers in the expression. Type an exact answer, using radicals as needed.)