Holt McDougal Geometry

1-5 Using Formulas in Geometry

BellworkWrite a definition of the angle pairs below,

and draw a diagram to represent each pair.

Holt McDougal Geometry

1-5 Using Formulas in Geometry

Apply formulas for perimeter, area, and circumference.

Rigor

RelevanceFormulas help determine the amount needed and cost of materials.

Holt McDougal Geometry

1-5 Using Formulas in Geometry

The perimeter (P) is the sum of the side lengths of the figure. Units for length (ft, m, in)

The area (A) is the number of square units of a given size that exactly cover the figure. Square units (ft2, m2, in2)

Holt McDougal Geometry

1-5 Using Formulas in Geometry

Rectangle

A = bhb=base, h=height

h

b

Triangles Circles

A = ½ bhA = r2

Circumference (C)C = 2r C = d

r = radiusd = diameter

Holt McDougal Geometry

1-5 Using Formulas in Geometry

The base b can be any side of a triangle. The height h is a segment from a vertex that forms a right angle with a line containing the base.

Holt McDougal Geometry

1-5 Using Formulas in Geometry

Find the perimeter and area of each figure.

Example 1: Finding Perimeter and Area

Holt McDougal Geometry

1-5 Using Formulas in Geometry

The Texas Treasures quilt block includes 24 purple triangles. The base and height of each triangle are about 3in. Find the approximate amount of fabric used to make the 24 triangles.

Example 2: Crafts Application

If the fabric costs $8 per square foot, how much will the fabric cost?

Holt McDougal Geometry

1-5 Using Formulas in Geometry

Example 3: Calculate the Circumference and Area of a Circle

Calculate C and A of the 12in pizza in terms of and to the nearest tenth.

Holt McDougal Geometry

1-5 Using Formulas in Geometry

Composite Figures• Composite figure– a region made of

common, non-overlapping shapes

• Area Addition Postulate – the area of a region is the sum of the areas of its non-overlapping parts

Holt McDougal Geometry

1-5 Using Formulas in Geometry

Example 4: Calculate the area of the shaded regions below.

Holt McDougal Geometry

1-5 Using Formulas in Geometry

Example 5: Real Life Application

A) If a runner were to run 4 laps on the outer track, about how far would he run? Use 3.14 for .

B) The school re-sods the grass inside the track. About how many square feet should the school buy? Use 3.14 for .

Holt McDougal Geometry

1-5 Using Formulas in Geometry

Classwork from the Textbook

Homework from the Core Book

Heading: Section 1-5 Classwork pg 38-39

Assignment: pg 38 #3 – 9pg 39 #20 – 22, 26, 30

Core book 1-5 Problem Solving: pg 30 #1 – 6

Due Thursday for periods 1, 3, & 5Due Friday for periods 2, 4, & 7