Circle geometry.notebook - St Leonard's College · 2012-09-03 · Circle geometry.notebook 2...
Transcript of Circle geometry.notebook - St Leonard's College · 2012-09-03 · Circle geometry.notebook 2...
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Circle Geometry Theorems
Theorem 1: The angle that an arc forms at the centre of a circle is twice the size of an angle formed at the circumference.
Theorem 2: The angle formed on the circumference from a diameter of a circle is always a right angle.
Theorem 3: All angles at the circumference standing on the same arc, in the same segment, are equal.
Theorem 4: The opposite angles in a cyclicquadrilateral add to 180 degrees.A cyclic quadrilateral is a quadrilateral in which all four vertices are on the same circumferenceof the one circle.
Theorem 5: Any tangent drawn on a circle meets the radius of the circle at right angles.
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Arc lengthThe length of the arc of a circle is a fraction of the circle's circumference.
C = 2 π rNow is a fraction of the circle. So,
(the arc length) is a fraction of the circumference
So =
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