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Warm up 30 80 100 180 100 260 Inscribed Angles and Inscribed Quadrilaterals Central Angle Central Angle = Arc Inscribed Angle •Angle where the vertex is ON the circle Inscribed Angle Inscribed Angle = intercepted Arc/2 ARC ANGLE = 2 160 80 The arc is twice as big as the angle!! Inscribed angles Find the value of x and y. 120 x y= = 120 60 Examples 1. If mJK = 80 and JMK = 2x – 4, find x. x = 22 2. If mMKS = 56, find m MS. 112 J K Q M S If two inscribed angles intercept the same arc, then they are congruent. A C B BAD =BCD D Find the measure of DOG ,DIG, ODI and OGI D 74 G O 102 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 mA mC 180 mB mD 180 If a right triangle is inscribed in a circle then the hypotenuse is the diameter of the circle. Example 3 In J, m3 = 5x and m 4 = 2x + 9. Find the value of x. 5x = 2x + 9 3x = + 9 x=3 Q D T 3 J 4 U Example 4 In K, GH is a diameter and mGNH = 4x – 14. Find the value of x. 4x – 14 = 90 4x = 104 G x = 26 H K N Example 5 Solve for x and z. 2x +18 + 22x – 6 = 180 24x +12 = 180 24x = 168 x=7 z + 85 = 180 z = 95 z 2x + 18 22x – 6 85 Textbook p. 420 #2 – 13 (omit #6), 17 – 20, 22