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