由于Δx=0.03很小
ƒ(xo+Δx)=ƒ(xo)+ƒ’(xo)Δx
所以y=arctan (1+0.03)= arctan 1 + 1/(1+x)²|(x=1) *0.03=π/4+1/4 *0.03=0.793