In the image, we are asked to find the length of segment $AD$ in the left circle, where point $A$ is the center of the circle.

We can infer the following details:

• The radius of the circle is the distance from the center $A$ to any point on the circumference.
• From the diagram, segment $AC = 4 \, \text{cm}$ represents the radius.
• Since $AD$ is also a radius (as $D$ lies on the circumference and $A$ is the center), the length of segment $AD$ is equal to the radius of the circle.

Thus, the length of segment $AD$ is 4 cm.

Would you like more explanation or help with a related problem?

Here are five related questions for deeper understanding:

1. What is the total circumference of the circle with radius 4 cm?
2. How would you calculate the area of the left circle?
3. What is the relationship between the radius and the diameter of a circle?
4. If the radius doubled, what would be the new length of segment $AD$?
5. Can a chord be longer than the radius of a circle? Why or why not?

Tip: The radius of a circle is always constant, so any segment from the center to a point on the circle will always have the same length.