Geometry puzzle

123456789
Across
  1. 2. 3.1415926535898
  2. 5. a perfectly round, curved shape with no corners or angles
  3. 6. exactly half of a circle with an arc measuring 180 degrees
  4. 8. a chord that contains the center of the circle
  5. 9. A curved line representing a portion of the circumference of a circle
Down
  1. 1. a segment whose endpoints are the center and any point on a circle
  2. 3. A line that intersects a circle in two points
  3. 4. distance around a circle
  4. 5. the exact, fixed point in the middle of a circle. It serves as the reference point for the circle's radius and is the midpoint of any diameter.
  5. 7. a segment whose endpoints are on a circle