#### Transcript Chapter_4_Introduction_web

Chapter 4.1 - Classifying Triangles **Objective: ***To be able to identify and classify *

*triangles by their angles and sides.*

Check.4.9 Classify triangles, quadrilaterals, and polygons (regular, non-regular, convex and concave) using their properties. Check.4.10 Identify and apply properties and relationships of special figures (e.g., isosceles and equilateral triangles, family of quadrilaterals, polygons, and solids).

Classifying Triangles

**Classify by Angles**

• Acute Triangle • All angles < 90

**Classify by Sides**

• Scalene Triangle • No two sides are the same • Obtuse Triangle • One angle > 90 • Right Triangle • One angle = 90 • Isosceles Triangle • At

**least**

same two sides are the • Equilateral Triangle • All sides are the same

B Classify the Triangles A • •

**Acute Triangles**

ADB EDB C D • • • •

**Right Triangles**

ACD ABC DCE BCE E

**Obtuse Triangles**

• • ADE AEB

B Classify the Triangles A • •

**Isosceles Triangles**

ADB EDB

**Equilateral Triangles**

• none C D

**Scalene Triangles**

• • • AEB AED ACB • • • ACD BCD DCE E

R Find Missing Values in Triangle Find x and the measure of each side of the

**Equilateral Triangle**

RST if RS = x + 9, ST = 2x, and RT = 3x -9 S x + 9 2x x + 9 = 2x -x -x 9 = x 3x - 9 T RS = x + 9 = 9 + 9 = 18

K Find Missing Values in Triangle Find d and the measure of each side of the

**Equilateral Triangle**

KLM if KL = d + 2, LM = 12 - d, and KM = 4d -13 d + 2 L 4d -13 12 - d M d + 2 = 12 - d +d +d 2d + 2 = 12 -2 -2 2d = 10 d = 5 KL = d + 2 = 5 + 2 = 7

Use the distance formula • Find x and the measure of the sides of DEC. Classify the triangle by its sides

**C**

E(-5, 3) C (3, 9) D (2, 2)

**E D**

• Isosceles Triangle

Use the distance formula • Find x and the measure of the sides of RST. Classify the triangle by its sides

**T**

R(-1, -3) S (8, -1) T (4, 4)

**R S**

RS = √85 ST= √41 RT= √74 • Scalene Triangle

Practice Assignment • Block Page 239, 16 – 36 Every 4th and 44 • Honors page 239 30 – 52 Even