Cos^2 a + sin^2 a = 1
1) sin^2 a = 1 - (- 0.6)^2 = 0.64
sin a = ± 0,8
Так как pi < a < 3 pi/2
sin a = - 0.8
tan a = 0,8 / 0,6 = 8/6 = 1 1/3
ctg a = 0.6 / 0.8 = 2/3
--------------------------------------------------------
2) cos^2 a = 1 - 64/289 = 225/289
Так как 0 cos a = 15/17
tan a = 8/15
ctg a = 15/8