Circle Geometry Circle Rule 1

Inscirbed angles that are on the same arc or have two identical arcs are the same. Circle Rule 2

The central angle is twice the measure of the inscribed angle aslong as they are on the same arc. Circle Rule 3

A perpendicular bisector is a line from the centre to a cord at 90 degrees, and divides the cord into 2 equal parts. Circle Rule 4

A tangent is a line that touches a circle in only one spot and is 90 degrees to the radius. Vocab Circle

Round, no corners or strait edges. Circumferance

The lenght of the outside of a circle (perimeter) Diameter

The longest distance across a circle (A line through the centre of the circle) Radius

Half of the diameter of a circle, a line from the centre to the edge. Pi

A number used when talking about a circle (3.14) Arc

Part of the outside of a circle. Chord

A line from one spot on the circle to another spot on the circle. Central Angle

An angle formed by two ridii, an angle to the centre of a circle. Inscribed Angle

An angle formed by two chords Solving 90 degree triangles

We can use the pythagorean Theorem to find sides.

Formula- a2+b2=c2 Longest side (hypotienuse) across from the 90 degree angle is always c2. Ex. Toolbox (when using all circle rules to solve problems)

1) All angles of a triangle add up to 180 degrees. 2) All angles of a circle add to 360 degrees. 3) All angles of a line add to 180 degrees. 4) Isosceles triangle

two sides are the same so two angles are the same. Ex. Ex. Ex Ex Ex. The relationship between the perpendicular bisector and the chord is that the perpendicular bisector divides a chord into two equal parts. What is the measure of the inscribed angle?

To find the answer you would multiply 20 by 2 to get 40. What is the lenght of side C when it is on the perpendicular bisector?

To find the answer you would use the pythagoreon therom. What are the measures of the inscribed angles?

To find them you would figure out which angles are on the same arc. Such as what is shown here. the angles that are on the blue arc would be the same. 1) What is the lenght of diameter BD?

2) What is the lenght of chord BE?

3) What is the measure of the inscribed angle BED?

4)What is the lenght of chord DE? 1) Since it is a right triangle you would have to solve using the pythagoreon therom.

2) Since chord B to E is the same length as the rsdius you would have to split the diameter in half.

3) Angle BED is a right angle since it is attached to the diameter.

4) Since it is a right triangle you would use the pythagoreon therom to solve.

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