来自贺宏朝的问题
已知x→0时,(1+ax^2)^(1/3)-1与cosx-1是等价无穷小,则常数a=?
已知x→0时,(1+ax^2)^(1/3)-1与cosx-1是等价无穷小,则常数a=?
3回答
2020-06-24 21:57
已知x→0时,(1+ax^2)^(1/3)-1与cosx-1是等价无穷小,则常数a=?
已知x→0时,(1+ax^2)^(1/3)-1与cosx-1是等价无穷小,则常数a=?
x→0时,(1+ax^2)^(1/3)-1≈1+ax²/3-1=ax²/3
cosx-1≈1-½sin²x-1=½sin²x≈x²/2
ax²/3=x²/2
a=3/2
1+ax^2)^(1/3)-1≈1+ax²/3-1cosx-1≈1-½sin²x-1怎么的来的?
x趋向于0时等价无穷小替换(1+x)n∽1+nxsinx∽x