tan(b-pai/4)=sin(b-pai/4)/cos(b-pai/4)=1/4(根号2/2*sinb-根号2/2*cosb)/(根号2/2*cosb+根号2/2*sinb)=1/4(tanb-1)/(1+tanb)=1/4tanb=5/3tan(a+b)=sin(a+b)/cos(a+b)=2/5(cosa*sinb+sina*cosb)/(cosa*cosb-sina*si...