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Explore central and inscribed angles, semicircles, major and minor arcs in circles. Practice solving angles and arc measures. Learn about special properties in circles and quadrilaterals inscribed in circles.
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Unit 3A Circles
Assignment on Blog
Math II UNIT QUESTION: What special properties are found with the parts of a circle? Standard: MM2G1, MM2G2 Today’s Question: How are central angles different from inscribed angles? Standard: MM2G3.b
Case I:Vertex is AT the center A P C B
EDF Semicircle: An Arc that equals 180° To name: use 3 letters E D P F
Central Angle : vertex is at the center of the circle ACB AB A Major Arc Minor Arc More than 180° Less than 180° P C B
measure of an arc = measure of central angle m AB m ACB m AE A E 96 Q = 96° B C = 264° = 2x + 14 Find x. x = 35
Case II:Vertex is ON circle ANGLE ARC ARC ANGLE
160 The arc is twice as big as the angle!! 80
Find the value of x and y 120 x y
J K Q S M Examples 1. If m JK = 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
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 Bonus: What type of triangle is this? Why?
Classwork • Workbook Page 204 #12-24 • Workbook Page 218 & 219
a quadrilateral inscribed in a circle: opposite angles are supplementary. B A D C
Example 5 Find y and z. z 110 110 + y =180 y y = 70 85 z + 85 = 180 z = 95
Homework: • Page 193 #9-18, 21-27 • Page 207 #1-18