已知tanα＝-8/15,且π/2＜α＜π,则cosα等于多少?sinα等于多少?

Question

已知tan α＝-8/15,且π/2＜α＜π,则cos α等于多少?sin α等于多少?

Answer 1

tan α = sin α/cos α = -8/15 ---(1)
sin α^2+cos α^2 = 1 ---(2)
∵π/2＜α＜π,∴sin α>0, cos α