PSSA Coach Lesson 14

CirclesM11.C.1.1.1M11.C.1.1.2

Unit 3: Geometry

Key ConceptsDefinitions relating to a circle:

◦Circle: all points in a plane that are equidistant from one point, the center.

◦Radius: a segment form the center to one point on a circle.

◦A chord is a segment with both endpoints on the circle.

◦Diameter: a chord that passes through the center of the circle.

◦A central angle is an angle whose vertex is the center of the circle.

Key ConceptsThe central angle forms a minor

arc and a major arc. Arcs, like circles, are measured in degrees.◦The degree measure of a major arc is

equal to 360˚ - the degree measure of its minor arc.

◦The degree of a minor arc is equal to the measure of its central angle.

◦The length of arc l = (D/360) * 2πr; where r is the radius and D is the measure in degree of the arc.

Key ConceptsSemi-circle is a half circle.A tangent is a line in the same

plane as a circle that touches the circle at one point.

An inscribed angle is an angle whose vertex is on the circle and whose sides are chords of the circle. ◦The outer angle is two times as great the inscribed angle.

Key Concepts Square ABCD is inscribed in

circle O. Assume that the radius of the circle

is 4cm.

◦Finda. mLAOBb. mABc. length of BCd. length of BAC

Key ConceptsExample 2:

◦PM is a tangent line to circle O and point M.

◦Find LOMP.◦Find OP.

Independent Practice Do “Check it out with the Coach”

on Pg 163.

◦Take about 3 minutes on your own, then we will discuss it.

Now Do…Do Lesson 14 Practice on

Pgs. 164-165#1-9all ◦SHOW ALL WORK!!!!

NO WORK = NO CREDIT ◦For the open-ended: Write your

response and justify the for answer with a sentence!!!