tan(a+b)=2/5,tan(b
tan(a+π/4) =tan[(a+b)-(b-π/4)] =[tan(a+b)-tan(b-π/4)]/[1+tan(a+b)*tan(b-π/4)] =[(2/5)-(1/4)]/[1+(2/5)*(1/4)] =3/22.