例4求函数y= loga x的导数 解∵x=a"在I,∈(-∞,+∞内单调、可导, 且(a3)=a"na≠0,∴在Ix∈(0,+∞)内有, (oga x) (a) a Ina xIna 特别地(nx)= Economic-mathematics 31-7 Wednesday, February 24 2021Economic-mathematics 31 - 7 Wednesday, February 24, 2021 例4 求函数 y log x的导数. = a (a ) = a lna  0, 且 y y 在 (0,+)内有, x I ( ) 1 (log )   = a y a x a a y ln 1 = . ln 1 x a = 解 = 在 (− ,+ )内单调、可导, y y  x a I 特别地 . 1 (ln ) x x  =