Arcs
Let’s start by saying the measurement of the minor arc is 110 degrees while the measurement of the major arc is 250. By knowing both of the degrees of each arch we can start to find the arc lengths by multiplying the circumference by the central angle (in degrees) divided by the whole degree of the circle which is 360 degrees. This is the same formula. When using this formula make sure the central angle used is the angle that is created by two radii that extend out creating the arc.
external image 300px-Circle_arc.svg.png external image arc_85degrees_CCCCFF.jpg
Formula to find the Arc
2π(Radius) Central Angle
.......................360.......................


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Inscribed Angles

An Inscribed Angle is an angle whose vertex is on the circle and whose sides each contain chords of the circle.

Theorem 9-4
If an angle is inscribed in a circle, then the measure of the angle equals one-half the measure of its intercepted arc.

Theorem 9-5

If two inscribed angles of a circle or congruent circles intercept congruent arcs or the same arc, then the angles are congruent.

Picture_4.png external image geo_cia.gif

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Chords

A chord of a circle is a segment that has its endpoints on the circle. The diameter is a chord. Even though it is not named a chord it is still one. It is not an ordinary chord, but a special cord that goes through the center point. A chord is basically a segment that is inside a circle.

external image 030309-2202-geometrynot1.png?w=231&h=225 external image chord_of_a_cirlce.jpg external image picture-tangent-chord-angle.jpg

FH is a cord -------------------------------------------- AB is a chord--------------------------------- AC is a chord. The special chord since its the diameter.

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