冪函數(shù)的情況比較復(fù)雜,不一定每個冪函數(shù)都有反函數(shù)
例1 y=x^2,沒有反函數(shù)
例2 y=x^3,有反函數(shù),y=x^(1/3)
例3 y=x^(1/2),有反函數(shù),y=x^2(x>=0)
小結(jié)：如果冪函數(shù)是偶函數(shù),則沒有反函數(shù)
如果冪函數(shù)是奇函數(shù),則有反函數(shù)
如果有反函數(shù),這個反函數(shù)也是冪函數(shù)