The Many Parts of a Circle

1. A B T The Many Parts of a Circle Secant Chord Tangent

2. Chords and Diameters: • Points on a circle can be connected by segments called chords. • A chord of a circle is a segment joining any two points on the circle. • A diameter of a circle is a chord that passes through the center of the circle. • The longest chord of a circle is the diameter. chord diameter

3. A B Secant A secant is a line that intersects a circle at exactly two points. (Every secant contains a chord of the circle.)

4. T Tangent A tangent is a line that intersects a circle at exactly one point. This point is called the point of tangency or point of contact.

5. Arcs of a circle • The arc of a circle is the section on the circle between two given points. • The symbol for an arc is m Arc AB = 60º This is a minor arc, it is less than half of the circle. 60º A B Arc ACB is a major arc. It measures 360 – 60 or 300 º C

6. Central Angle • Central angle: an angle where the vertex is the center of the circle. • It’s measure is the same measure as the arc it intersects. A B <ACB is a central angle Arc AB measures 65º Therefore m<ACB = 65 º C See AIMS Reference Sheet

7. Inscribed angle • An inscribed angle is an angle where the vertex is on the circle. • It’s measure is ½ the arc of the circle it intersects. 50º T <CAT is an inscribed angle. Arc CT measures 50º Therefore m<CAT = ½ of arc CT m<CAT = 25º C A See AIMS Reference Sheet