y' = f'(tanx + xlnx) [sec^2 x + lnx + 1]
y'' = f''(tanx + xlnx) [sec^2 x + lnx + 1]^2 + f'(tanx + xlnx) [2sec^2 x tanx+ 1/x]
思路:用复合函数求导方法.
y' = f'(tanx + xlnx) [sec^2 x + lnx + 1]
y'' = f''(tanx + xlnx) [sec^2 x + lnx + 1]^2 + f'(tanx + xlnx) [2sec^2 x tanx+ 1/x]
思路:用复合函数求导方法.