sin(a-pai/4)=√2/2(sinα-cosα)=7根号2/10
sinα-cosα=7/5
cos2a=1-2sin^2a=7/25 sina=正负3/5,cosa=正负4/5,tana=正负3/4
tan(a+pai/3) =(√3+tana)/(1-√3tana)=(4√3+3)/(4-3√3) 或(4√3-3)/(4+3√3)
sin(a-pai/4)=√2/2(sinα-cosα)=7根号2/10
sinα-cosα=7/5
cos2a=1-2sin^2a=7/25 sina=正负3/5,cosa=正负4/5,tana=正负3/4
tan(a+pai/3) =(√3+tana)/(1-√3tana)=(4√3+3)/(4-3√3) 或(4√3-3)/(4+3√3)