已知sina+cosa=1\5a∈（0,π）,求tana,sina-cosa,sin^3+cos^3的值

(sina+cosa)^2=1/25 ,2sinacosa=-24/25
(sina-cosa)^2=1-2sinacosa=1+24/25=49/25
sina-cosa=7/5 ,a∈（0,π）,
sina+cosa=1/5 ,√[1-(cosa)^2]=1/5-cosa
1-(cosa)^2=1/25-2cosa/5+(cosa)^2
(cosa)^2-cosa/5-12/25=0
cosa=[1/5-√(1/25+48/25)]/2
=-3/5 ,sina=4/5
tana=-4/3
sin^3a+cos^3a=(4/5)^3+(-3/5)^3
=37/125