已知sin(π/2+α)-cos(3π/2-α)=1/5(π/2

已知sin(π/2+α)-cos(3π/2-α)=1/5(π/2
已知sin(π/2+α)-cos(3π/2-α)=1/5(π/2

已知sin(π/2+α)-cos(3π/2-α)=1/5(π/2
==》cosa+sina=1/5

cos^a+2cosasina+sin^a=1+2cosasina=1/25
cosasina=-12/25

cosa<0,-sina<0 1-2cosasina=(cosa-sina)^=49/25
cosa-sina=-7/25

tana=sina/cosa=-12/2=-6