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Checking the three-part continuity test at x = 0

Consider the piecewise function p(x)={sin⁡(x)xx≠00x=0p(x) = \begin{cases} \dfrac{\sin(x)}{x} & x \neq 0 \\ 0 & x = 0 \end{cases} You may use the known fact that lim⁡x→0sin⁡(x)x=1\lim_{x \to 0} \dfrac{\sin(x)}{x} = 1.

Using the three-part definition of continuity, determine whether p(x)p(x) is continuous at x=0x = 0. Explicitly state the value of p(0)p(0), the value of lim⁡x→0p(x)\lim_{x \to 0} p(x), and whether these two values are equal. Based on this, is pp continuous at x=0x=0, and if not, which of the three continuity conditions fails and what type of discontinuity (removable, jump, or infinite) occurs there?

Hint

Evaluate p(0)p(0) directly from the definition, then use the given fact lim⁡x→0sin⁡(x)/x=1\lim_{x\to 0}\sin(x)/x = 1 to find the limit. Compare the two numbers to check the third condition of continuity.

Step-by-step solution

First check condition 1: is p(0)p(0) defined? By the definition of the piecewise function, p(0)=0p(0) = 0, so this condition is satisfied. Next check condition 2: does lim⁡x→0p(x)\lim_{x\to 0} p(x) exist? Since p(x)=sin⁡(x)/xp(x) = \sin(x)/x for all x≠0x \neq 0 near 00, and we are given that lim⁡x→0sin⁡(x)/x=1\lim_{x\to 0} \sin(x)/x = 1, the limit exists and equals 11.

Finally check condition 3: does lim⁡x→0p(x)=p(0)\lim_{x\to 0} p(x) = p(0)? We found lim⁡x→0p(x)=1\lim_{x\to 0}p(x) = 1 but p(0)=0p(0) = 0, so these values are not equal. Therefore condition 3 fails, and pp is not continuous at x=0x=0. Since the limit exists but does not match the function value, this is a removable discontinuity — the graph has a hole at (0,0)(0,0) that could be patched by redefining p(0)=1p(0) = 1.

Checking the three-part continuity test at x = 0 — solution graph

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