Day 19 AGENDA: DG 10 --- 15 minutes Workday on CLT & Conf Int --- 20 min Begin Unit 2 --- Algebra Topics

Unit #2: Algebra Topics Lesson 1: Review of Circles Accel Precalculus Unit #2: Algebra Topics Lesson 1: Review of Circles EQ: What is the equation of a circle and how do you use it to graph a circle?

(h, k) r Conic Sections in Algebra: Circle --- the set of all points in a plane that are a common distance , called the radius, from a fixed point, called the center. (h, k) center: _________ r radius: ______

An equation for the circle with its center at Standard Equation of a Circle: An equation for the circle with its center at (0, 0) and a radius of r is Standard Equation of a Translated Circle: The standard equation for circle with its center at (h, k) and a radius of r is

Ex. 3 A cell phone tower is located 25 miles east and 30 miles south of Lorne’s home. The tower’s signal is strong enough to reach phones within a 50 miles radius. Write the equation that represents all ground locations 50 miles from the cell phone tower given that Lorne’s home is located at (0,0).

Can a person living 10 miles east and 5 miles north of Lorne receive the tower’s signal? Houses receiving phone reception are found using the following inequality. WHY? The person’s home located 10 miles east and 5 miles north must be located within this circle.

RECALL: COMPLETING THE SQUARE

In class practice. 1. Write the standard form of the circle graphed at the right.

2. Graph (x - 1)2 + (y - 5)2 = 4

(3, 4) 6 (3, 2) 5 3. Find the center and radius of the circle with the given equation. a. (3, 4) 6 center: _________ radius: ______ b. center: _________ radius: ______ (3, 2) 5

ASSIGNMENT : Worksheet: Review of Circles #9, 10, 12, 17, 19, 28, 44, 47, 49, 68, 73, 78