00cosa=3/5 (sina)^2+(cosa)^2=1 (sina)^2=1-(cosa)^2=1-3/5*3/5=16/25sina=4/5, tana=sina/cosa=(4/5)/(3/5)=4/3cos2a+sin(π/2-a)=(cosa)^2-(sina)^2+cosa=3/5*3/5-4/5*4/5+3/5=9/25-16/25+15/25=8/25
