Jawaban No.1 Sudut Ganda Trigonometri

1. a. sin (2A+A)       = Sin 2A cos A + cos 2A sin A

                   = (2 Sin A cos A) cos A + (1 – 2 sin ²A) sin A

                   = 2. 8/17 . (-15/17)² + (1 – 2(8/17)²) 8/17 = 3600/4913 + 1288/4913

                   = 4888/4913

b. cos 2A = cos² A – sin² A = (- 15/17)² – (8/17)² = 225/289 – 64/289 = 161/289=

atau

cos 2A = 1 – 2 sin² A = 1 – 2 (8/17)² = 1 – 128/289 = 161/289

atau

cos 2A = 2 cos² A – 1 = 2. (- 15/17)² – 1 = 450/289 – 289/289 = 161/289