x趋向于零,sin2x^3与4x(1-cosx)是等价无穷小?(sinx)^2与6xsinx是同价无穷小?
问题描述:
x趋向于零,sin2x^3与4x(1-cosx)是等价无穷小?(sinx)^2与6xsinx是同价无穷小?
答
(1)sin2x^3 与 2x^3等价
4x(1-cosx)=4x*(sinx)^2/(1+cosx) 与 4x*x^2/2=2x^3等价
故sin2x^3与4x(1-cosx)是等价无穷小
(2)(sinx)^2与x^2等价
6xsinx与6x^2等价
故 (sinx)^2与6xsinx是同阶无穷小
答
sin2x^3~2x^3
4x(1-cosx)~4x*1/2*x^2=2x^3
故sin2x^3与4x(1-cosx)是等价无穷小
(sinx)^2~x^2
6xsinx~6x^2
(sinx)^2与6xsinx是同价无穷小