Final answer:
The difference of the lengths of BC and CE is given by the expression BC - CE, but we need more information to calculate it.
Step-by-step explanation:
The difference of the lengths of BC and CE is given by the expression BC - CE. To find this difference, we need to know the lengths of BC and CE.
Based on the information provided, we have a circle with a radius of r and an arc length of a. The length of the baseline BC is approximately equal to the length of the corresponding arc, which is a. Therefore, BC = a.
On the other hand, CE is not given directly in the information provided. We need more information to determine the length of CE. Without that information, we cannot calculate the difference BC - CE.