Mathematics

Mathematics

Problem

Find the limit, or state that it does not exist, for lim⁡x→0ln⁡(1+x)−sin⁡xx3.\displaystyle \lim_{x\to 0} \frac{\ln(1+x)-\sin x}{x^{3}}.
Intuitive explanation

This limit tests whether you can distinguish between functions that look similar near zero. Both ln⁡(1+x)\ln(1+x) and sin⁡x\sin x approach 0 as x→0x \to 0, so you'll get the indeterminate form 00\frac{0}{0}—the key is to expand both using Taylor series and see which terms survive after cancellation. Once you subtract them in the numerator, you'll find the lowest-order term that doesn't vanish, then divide by x3x^3 to find the limit.

Intuitive explanation

This limit tests whether you can distinguish between functions that look similar near zero. Both ln⁡(1+x)\ln(1+x) and sin⁡x\sin x approach 0 as x→0x \to 0, so you'll get the indeterminate form 00\frac{0}{0}—the key is to expand both using Taylor series and see which terms survive after cancellation. Once you subtract them in the numerator, you'll find the lowest-order term that doesn't vanish, then divide by x3x^3 to find the limit.

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