220 likes | 335 Vues
This lesson focuses on the properties of inscribed angles and their relationship to intercepted arcs in circles. We explore how to locate a gazebo among three houses using geometric centers, identify inscribed angles, and calculate their measures. Students will learn that the measure of an inscribed angle is half the measure of its intercepted arc. The homework will consist of practice problems to reinforce these concepts, including the relationship between angles and arcs, and properties of inscribed and circumscribed polygons.
E N D
Warm-up Find the measure of each arc.
A gazebo is to be constructed between three houses so that it will approximately be the same distance from each house. Which would be helpful in deciding where to locate the gazebo? EOCT Review a) Centroid b) Circumenter c) Incenter d) Orthocenter b
CCGPS GeometryDay 21 (9-5-13) UNIT QUESTION: What special properties are found with the parts of a circle? Standard: MMC9-12.G.C.1-5,G.GMD.1-3 Today’s Question: How do we use angle measures to find measures of arcs? Standard: MMC9-12.G.C.2
Inscribed Angle: An angle whose vertex is on the circle and whose sides are chords of the circle INTERCEPTEDARC INSCRIBEDANGLE
YES; CL C T O L Determine whether each angle is an inscribed angle. Name the intercepted arc for the angle. 1.
NO; QVR Determine whether each angle is an inscribed angle. Name the intercepted arc for the angle. 2. Q V K R S
What do we call this type of angle? What is the value of x? What do we call this type of angle? How do we solve for y? The measure of the inscribed angle is HALF the measure of the inscribed arc!! 120 x y
J K Q S M Examples 3. If m JK = 80, find mJMK. 40 4. If mMKS = 56, find m MS. 112
If two inscribed angles intercept the same arc, then they are congruent. 72
Q D 3 J T 4 U Example 5 In J, m3 = 5x and m 4 = 2x + 9. Find the value of x. x = 3
If all the vertices of a polygon touch the edge of the circle, the polygon is INSCRIBED and the circle is CIRCUMSCRIBED.
A circle can be circumscribed around a quadrilateral if and only if its opposite angles are supplementary. B A D C
Example 8 Find y and z. z 110 110 + y =180 y y = 70 85 z + 85 = 180 z = 95
If a right triangle is inscribed in a circle then the hypotenuse is the diameter of the circle. 180 diameter
Example 6 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 7 In K, m1 = 6x – 5 and m2 = 3x – 4. Find the value of x. 6x – 5 + 3x – 4 = 90 H 2 K x = 11 N 1 G
Practice Worksheet
Homework: • Worksheet