If f(x)=xTan−1x then Ltx→1f(x)−f(1)x−1=
π4
π+14
π+24
π+34
limx→1 f(x)-f(1)x-1=0/0 use L hospital rule limx→1 f1(x)-01-0=f1(1) f(x)=xtan-1x⇒f1(x)=x1+x2+tan-1x f1(1)=12+π4