tg a = sin a/cos a
cos^2 a = 1 - sin^2 a = 1 - (-3/5)^2 = 1 - 9/25 = 16/25 получается cos a = 4/5
tg a = -3/5 : 4/5 = -3/5 * 5/4 = -3/4
tg a = sin a/cos a
cos^2 a = 1 - sin^2 a = 1 - (-3/5)^2 = 1 - 9/25 = 16/25 получается cos a = 4/5
tg a = -3/5 : 4/5 = -3/5 * 5/4 = -3/4