соs²a + sin²a = 1, следовательно sin²a = 1 - cos²a
sin²a = 1 - 64/289
sin²a = 289/289 - 64/289 = 225/289
sin a = 15/17
tg = sin/cos
tg = 15/17 ÷ 8/17 = 15/8
ctg = соs/sin
ctg = 8/17 ÷ 15/17 = 15/8 = 1,875
соs²a + sin²a = 1, следовательно sin²a = 1 - cos²a
sin²a = 1 - 64/289
sin²a = 289/289 - 64/289 = 225/289
sin a = 15/17
tg = sin/cos
tg = 15/17 ÷ 8/17 = 15/8
ctg = соs/sin
ctg = 8/17 ÷ 15/17 = 15/8 = 1,875