Area and Circumference

5-4-09

IMP3

Sia

Today’s Agenda

Bell ringer, seating chart Collect take-home quizzes Go over HW Area and circumference formulas for

circles HW16 p. 105 (in green book) due

Friday, May 8th

Announcements ACT session on Saturday, May 30th in room 208

from 8am-10am HW16 p. 105 from green book is due Friday, May

8th HW Hall this Thursday during 9th period (not

Tuesday) Return your graphing calculator to Ms. Sia by this

Friday, May 8th # of students who completed last week’s HW:

3rd period: 6 out of 24 (25%) 4th period: 4 out of 17 (24%) 5th period: 3 out of 17 (18%)

Remember…

HW is due at the end of every week. Quizzes will be during class every

Friday. You are to sit in your assigned seat. All necessary information to complete

class work is in your notes or geometry packets.

Orchard Hideout Last week, you needed

to read p. 60-61 to know what the unit is about.

We’re not doing all of the unit, but several HW assignments are from the unit.

This week: Use area and circumference formulas to answer problems on HW16 p. 105

This week’s vocabulary

Circle Center Radius Area Circumference Arc Sector 360°

Area of Circles

Area describes the amount of space an object takes up.

For circles, to find its area, take the radius, square it, then multiply by pi.

Circumference

Circumference describes the distance around a circle.

Circumference is simply the perimeter of a circle.

Arc

An arc has two points on a circle and all the points of the circle needed to connect those two points.

We say “arc AB”

Sector

A sector of a circle is a region bounded by two radii and an arc of a circle.

Exact vs. Approximate Example: Find the circumference of a circle with

radius 7.EXACT:C = 2r = 2(7) = 14

APPROXIMATE:C = 2r = 2(7) = 14 = 43.98

I will let you know whether I want exact or approximate answers for your class work.For this week’s HW, use EXACT ANSWERS.