1.f(x)=f(x0)+f'(x0)(x-x0),f(x)=x^0.5,x0=1
=1+0.5*0.05=1.025
2.f(x)=tanx,f(x0)=tan45=1
=1+sec^(-2)*(π/4)×π/180=1+0.035=1.035
3.f(x)=lnx ,x0=1
=ln1+1*0.002=0.002