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Explore the fascinating relationship between inscribed angles and central angles in circles! This guide covers key concepts including the inscribed angle theorem, where the measure of an inscribed angle is half that of the central angle subtending the same arc. Learn how to calculate unknown angles in triangles inscribed in circles, and the properties of inscribed polygons. With numerous examples and practice problems, you will reinforce your understanding of these important geometric principles. Ideal for students seeking to master the topic in geometry.
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Warm up 30 80 100 180 100 260
Central Angle Angle = Arc
Inscribed Angle • Angle where the vertex is ON the circle
160 The arc is twice as big as the angle!! 80
Find the value of x and y. 120 120 x 60 y
J K Q S M Examples 1. If mJK= 80 and JMK = 2x – 4, find x. x = 22 2. If mMKS= 56, find m MS. 112
Find the measure of DOG and DIG D 72˚ G If two inscribed angles intercept the same arc, then they are congruent. O I
If all the vertices of a polygon touch the edge of the circle, the polygon is INSCRIBED and the circle is CIRCUMSCRIBED.
Quadrilateral inscribed in a circle: opposite angles are SUPPLEMENTARY B A D C
If a right triangle is inscribed in a circle then the hypotenuse is the diameter of the circle. diameter
Q D 3 J T 4 U Example 3 In J, m3 = 5x and m 4 = 2x + 9. Find the value of x. x = 3
Example 4 In K, GH is a diameter and mGNH = 4x – 14. Find the value of x. 4x – 14 = 90 H K x = 26 N G
Example 5 Find y and z. z 110 110 + y =180 y y = 70 85 z + 85 = 180 z = 95
Practice WS 10 problems
Homework WS 6.4 Practice