Question

已知,tana=-4/3,求sinA-3cosA/sinA+cosA的值

Answer 1

tana=-4/3,
sinA-3cosA/sinA+cosA
=(tana-3)/(tana+1)(分子分母同除cosA得）
=(-4/3-3)/(1-4/3)
=13

Answer 2

,tana=-4/3 , 3sinA=-4cosA , 9sin^2A=16cos^2A=16-16sin^2A, sin^2A=16/25, sinA=±4/5
sinA-3cosA/sinA+cosA
=sinA-3cotA-3/4sinA
=1/4sinA+9/4
=±1/5+9/4
=49//20或41/20