if tan A=24/7 and 180°
问题描述：
if tan A=24/7 and 180°
答
-3/5过程能写出来吗?摆脱啦~tan is opposite over adjacent, so we can let opposite = 24 and adjacent = 7 but since the angle is in quadrant 3, so opposite = -24 and adjacent = -7 due to pythagorean theorem, hypotenuse = 25. so, cos(A) = adjacent over hypotenuse = -7/25 double-angle formula: cos(x) = 2cos(x/2)^2-1 so: cos(A/2)^2 = (cos(A)+1)/2 = 9/25 so: cos(A/2) = 3/5 or -3/5 since 180°