− ex=k=0∑nk!xk=1+x+2x2+6x3+⋯+n!xn+o(xn)− sin(x)=k=0∑n(2k+1)!(−1)k⋅x2k+1+o(x2n+1)=x−6x3+120x5+⋯+(2n+1)!(−1)n⋅x2n+1+o(x2n+1)− cos(x)=k=0∑n(2k)!(−1)k⋅x2k+o(x2n)=1−2x2+24x4+⋯+(2n)!(−1)n⋅x2n+o(x2n)− 1−x1=k=0∑nxk+o(xn)=1+x+x2+x3+⋅+xn+o(xn)− log(1+x)=k=0∑n(2k+1)!(−1)k⋅x2k+1+o(x2n+1)=x−6x3+120x5+⋯+(2n+1)!(−1)n⋅x2n+1+o(x2n+1)