GMAT Exam: A Simple Guide To Geometry - Circles

Parts of a Circle
- circle is a closed plane figure for which all points are the same distance from the center within the circle.

- radius is a line segment joining the center of the circle to any point on the circle.

- diameter is a line segment through the center of the circle with endpoints on the circle.
The diameter of a circle is twice the radius.
Equivalently, the radius of a circle is half the diameter.

- chord of a circle is a line segment whose endpoints lie on the circle.


Useful Information About Circles

- If a radius is drawn so that it is perpendicular to a chord, it bisects the chord.


- An angle inscribed in a semicircle is a right angle.


- If two chords intersect within a circle, the product of the lengths of the segments formed for one chord equals the product of the lengths of the segments formed for the other chord.