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Exercise 717Calculus › Single-variable calculus › LimitsL1Added 1 Nov 2026

x ln x at zero, and x^x

#indeterminate forms#change of variable#logarithm

Statement

  1. Compute lim⁡x→0+xln⁡x\displaystyle\lim_{x\to0^+}x\ln x.
  2. Deduce lim⁡x→0+xx\displaystyle\lim_{x\to0^+}x^x.
Hint

Set y=1xy=\frac1x.

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Solution

1. The product xln⁡xx\ln x has the form 0×(−∞)0\times(-\infty), which is indeterminate. Put y=1xy=\frac1x; when x→0+x\to0^+, y→+∞y\to+\infty, and
xln⁡x=1yln⁡1y=−ln⁡yy⟶0.x\ln x=\frac1y\ln\frac1y=-\frac{\ln y}{y}\longrightarrow0.

2. For x>0x>0, xx=exln⁡xx^x=e^{x\ln x}. The exponent tends to 00, and exp⁡\exp is continuous, so
lim⁡x→0+xx=e0=1.\lim_{x\to0^+}x^x=e^0=1.

Remark. This is why one defines 00=10^0=1 in many contexts: the function xxx^x extends continuously to 00 with the value 11.