2.4 Circles

  • Properties of Circles • Tangent Secant Lines • Circumference Area • Circular Arcs Angles • Radian Measure of an Angle

The next geometric figure we consider is the circle. All points on a circle are at the same distance from a fixed point, the center of the circle. The distance from the center to a point on the circle is the radius of the circle. The distance between two points on the circle on a line through the center is the diameter. Therefore, the diameter d is twice the radius r, or d = 2r .  See Fig. 2.76.

A diagram of a circle. A line segment that goes from one point on the circle to another point while passing through the center is the diameter. Each half of the diameter is a radius.

Fig. 2.76

There are also certain types of lines associated with a circle. A chord is a line segment having its endpoints ...

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