по данному значению функции найдите значение других тригонометрических функций tg a

Cos a= -5/13pi/2 lt; a lt; pisin a = v 1-cos^2 = v 1-(-5/13)^2 = 12/13tg a = sin /cos = -5/13  / 12/13 = -5/12ctg a = 1 / tg a = 1/ -5/12 = - 2,4a)sin a = -0.83pi/2 lt; a lt; 2picos a = v 1-sin^2 = v 1- (-0.8)^2 = 0.6tg a = sin /cos = -0.8/0.6 = - 4/3ctg a = 1 / tg a = 1/ - 4/3 = -3/4 b)sin a = v3/3pi/2 lt; a lt; picos a = v 1-sin^2 = v 1- (v3/3)^2 = -v(2/3)tg a = sin /cos = v3/3 / -v(2/3) = -1/v2 = -v2/2ctg a = 1 / tg a = 1 / -1/v2 = -v2 b)cos a= 1/70 lt; a lt; pi/2sin a = v 1-cos^2 = v 1- (1/7)^2 = 4v3/7tg a = sin /cos = 4v3/7  /  1/7 = 4v3ctg a = 1 / tg a = 1/  4v3 = v3/12