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

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

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

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. T

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 A B m Arc AB = 60º This is a minor arc, it is less than half of the circle. 60º C Arc ACB is a major arc. It measures 360 – 60 or 300 º

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 C <ACB is a central angle Arc AB measures 65º Therefore m<ACB = 65 º See AIMS Reference Sheet

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. T A C 50º <CAT is an inscribed angle. Arc CT measures 50º Therefore m<CAT = ½ of arc CT m<CAT = 25º See AIMS Reference Sheet