cos2α =7/25=1-2sin^2a ,2sin^2a=1-7/25=18/25 ,sina=±3/5
sin（α -π/4）=(√2/2)(sina-cosa)=7√2/10 ,sina-cosa=7/5 ,cosa=4/5 ,tana=±3/4
tan（α +π/3）=(tana+tanπ/3)/(1-tanatanπ/3)
=(3/4+√3)/(1-3√3/4)或（ -3/4+√3)/(1+3√3/4)