## Algebra and Trigonometry 10th Edition

cos(2u) = $cos^{2}u - sin^{2}u = 2cos^{2}u - 1 = 1- 2sin^{2}u$
cos(2u) = $cos^{2}u - sin^{2}u = 2cos^{2}u - 1 = 1- 2sin^{2}u$ From the Double-Angle Formula