無窮小量
定義
![等價無窮小量](/img/5/4d8/nBnauM3X2MzN5UzM2MzNwIDN0UTMyITNykTO0EDMwAjMwUzLzczL4MzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![等價無窮小量](/img/c/d23/nBnauM3X1cTNxYzNzIjN0YzM1UTM1QDN5MjM5ADMwAjMwUzLyYzLzQzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
設 在某 上有定義。若
![等價無窮小量](/img/1/5ed/nBnauM3XzcTMxkDNwkzN0YzM1UTM1QDN5MjM5ADMwAjMwUzL5czL4czLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
![等價無窮小量](/img/5/4d8/nBnauM3X2MzN5UzM2MzNwIDN0UTMyITNykTO0EDMwAjMwUzLzczL4MzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![等價無窮小量](/img/a/02e/nBnauM3X1gTM5cDO2YTMzEzM1UTM1QDN5MjM5ADMwAjMwUzL2EzL1UzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
則稱 為當 時的無窮小量。
![等價無窮小量](/img/a/845/nBnauM3X1gTM1MTO3QzN0YzM1UTM1QDN5MjM5ADMwAjMwUzL0czLwQzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
![等價無窮小量](/img/1/fc7/nBnauM3X1UjNzgzN1ATOxADN0UTMyITNykTO0EDMwAjMwUzLwkzL3YzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
類似地可以定義當 以及 時的無窮小量。
性質
(1)兩個(相同類型的)無窮小量之和、差、積仍為無窮小量。
(2)無窮小量與有界量的乘積為無窮小量。
等價無窮小量
定義
![等價無窮小量](/img/a/02e/nBnauM3X1gTM5cDO2YTMzEzM1UTM1QDN5MjM5ADMwAjMwUzL2EzL1UzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
![等價無窮小量](/img/5/4d8/nBnauM3X2MzN5UzM2MzNwIDN0UTMyITNykTO0EDMwAjMwUzLzczL4MzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![等價無窮小量](/img/3/b02/nBnauM3XyATN5UjM4QTOwADN0UTMyITNykTO0EDMwAjMwUzL0kzL1AzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
設當 時, 與 均為無窮小量。若
![等價無窮小量](/img/8/f10/nBnauM3XyUTM3EDO5ADO0YzM1UTM1QDN5MjM5ADMwAjMwUzLwgzLwgzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
![等價無窮小量](/img/5/4d8/nBnauM3X2MzN5UzM2MzNwIDN0UTMyITNykTO0EDMwAjMwUzLzczL4MzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![等價無窮小量](/img/3/b02/nBnauM3XyATN5UjM4QTOwADN0UTMyITNykTO0EDMwAjMwUzL0kzL1AzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
![等價無窮小量](/img/a/02e/nBnauM3X1gTM5cDO2YTMzEzM1UTM1QDN5MjM5ADMwAjMwUzL2EzL1UzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
則稱 與 是當 時的等價無窮小量 。記作
![等價無窮小量](/img/b/1e8/nBnauM3X2UzNzMDO2MjN0YzM1UTM1QDN5MjM5ADMwAjMwUzLzYzL2gzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
性質
![等價無窮小量](/img/5/7c6/nBnauM3XwYTOwgDM5QzN0YzM1UTM1QDN5MjM5ADMwAjMwUzL0czLyYzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
![等價無窮小量](/img/c/d23/nBnauM3X1cTNxYzNzIjN0YzM1UTM1QDN5MjM5ADMwAjMwUzLyYzLzQzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
設函式 在 上有定義,且有
![等價無窮小量](/img/b/1e8/nBnauM3X2UzNzMDO2MjN0YzM1UTM1QDN5MjM5ADMwAjMwUzLzYzL2gzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
![等價無窮小量](/img/c/d21/nBnauM3X0gTMzMzN0QTMzEzM1UTM1QDN5MjM5ADMwAjMwUzL0EzLxQzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
![等價無窮小量](/img/9/de0/nBnauM3X0MTMxETMyMTN0YzM1UTM1QDN5MjM5ADMwAjMwUzLzUzL0EzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
(1)若 ,則
![等價無窮小量](/img/f/5d1/nBnauM3XwcjN4QDN2UzMzEzM1UTM1QDN5MjM5ADMwAjMwUzL1MzL3EzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
![等價無窮小量](/img/4/7ac/nBnauM3X3gzNyQjN3kTN0YzM1UTM1QDN5MjM5ADMwAjMwUzL5UzL2UzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
(2)若 ,則
常用的等價無窮小量
![等價無窮小量](/img/5/4af/nBnauM3X4YDM5ITN3EzMzEzM1UTM1QDN5MjM5ADMwAjMwUzLxMzLyEzLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
(1)當 時,常用的等價無窮小量
![等價無窮小量](/img/3/e41/nBnauM3XwEjNwITNzcjN0YzM1UTM1QDN5MjM5ADMwAjMwUzL3YzLzAzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
![等價無窮小量](/img/a/f10/nBnauM3X1EjNzIDNyYjN0YzM1UTM1QDN5MjM5ADMwAjMwUzL2YzL2YzLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
![等價無窮小量](/img/5/4af/nBnauM3X4YDM5ITN3EzMzEzM1UTM1QDN5MjM5ADMwAjMwUzLxMzLyEzLt92YucmbvRWdo5Cd0FmLwE2LvoDc0RHa.jpg)
(2)當 時,由基本等價無窮小量派生常用等價無窮小量
![等價無窮小量](/img/3/999/nBnauM3XwYDO5IzM2EDO0YzM1UTM1QDN5MjM5ADMwAjMwUzLxgzLxUzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)
![等價無窮小量](/img/a/9ac/nBnauM3XyYjNyUDN2IjN0YzM1UTM1QDN5MjM5ADMwAjMwUzLyYzLzAzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
![等價無窮小量](/img/c/d27/nBnauM3X2gzMyQTM3gjN0YzM1UTM1QDN5MjM5ADMwAjMwUzL4YzLwgzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
![等價無窮小量](/img/3/f38/nBnauM3XzAzMyYDM5EjN0YzM1UTM1QDN5MjM5ADMwAjMwUzLxYzL1QzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
套用
![等價無窮小量](/img/f/f8a/nBnauM3X2EjMyQjN4ITN0YzM1UTM1QDN5MjM5ADMwAjMwUzLyUzLzUzLt92YucmbvRWdo5Cd0FmLyE2LvoDc0RHa.jpg)
(1)求極限
![等價無窮小量](/img/4/ec1/nBnauM3X4IDMzIDM4QzN0YzM1UTM1QDN5MjM5ADMwAjMwUzL0czLwEzLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
解:由 所以
![等價無窮小量](/img/2/260/nBnauM3XzEzNxMTNyIjN0YzM1UTM1QDN5MjM5ADMwAjMwUzLyYzL4IzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
![等價無窮小量](/img/2/e24/nBnauM3X3czN5IjN4gTN0YzM1UTM1QDN5MjM5ADMwAjMwUzL4UzLxczLt92YucmbvRWdo5Cd0FmLzE2LvoDc0RHa.jpg)
(2)求極限
![等價無窮小量](/img/2/e38/nBnauM3XwUDMyQDN5kzN0YzM1UTM1QDN5MjM5ADMwAjMwUzL5czL4EzLt92YucmbvRWdo5Cd0FmLxE2LvoDc0RHa.jpg)
解:由 可得
![等價無窮小量](/img/7/8f0/nBnauM3X2czN1ITMwITN0YzM1UTM1QDN5MjM5ADMwAjMwUzLyUzLxgzLt92YucmbvRWdo5Cd0FmL0E2LvoDc0RHa.jpg)