【正文】
2 (xn)′= nxn1(n∈ Q) 3 (sinx)′=cos x 4 (cosx)′= sinx =C(C是常數(shù) ),求 y′. 解: y=f(x)=C, y=f(x+Δ x)f(x)=CC=0, xy?? =0. Y′= C′= xyx ???? 0lim=0,∴ y′=0. =sinx,求 y′ 解: Δ y=sin(x+Δ x)sinx =sinxcosΔ x+cosxsinΔ xsinx, x xxxxxxy ? ??????? s i ns i nc osc oss i n , ∴ xyyx ?????? 0lim xxxxxxxxxxxxxxxxxxxxxxxxxxxc o s4)2(2s i n)s i n2(l i ms i nc o sl i m)2s i n2(s i nl i ms i nc o s)1( c o ss i nl i ms i ns i nc o sc o ss i nl i m22002000?????????????????