Classifying Triangles

Section 4.1

Warm UpClassify each angle as acute, obtuse, or right.

1. 2.

3.

4. If the perimeter is 47, find x and the lengths of the three sides.

A triangle is a 3 Sided polygon.

A polygon is a closed figure in a plane that is made up of segments, called sides., that intersect at points called vertices.

ΔCDE is made up of: Sides: Vertices: Angles:

The side opposite ∠C is: The angle opposite

segment CE is: The side opposite ∠E is:

Parts of: Equilateral Triangle

Right Triangle

Isosceles Triangle

Is it possible for a triangle to have: A) Two obtuse angles?

B) Two right angles?

C) one right and one obtuse angle?

D) two acute and one obtuse angle?

ΔBLM is isosceles with base ML.

Identify an acute angle. Name the hypotenuse. Name the vertex angle. Name the side opposite ∠C. Name the angle opposite segment ML. Name the base angles. Name the vertices of the right triangle. Name the legs of the isosceles triangle.

1. ΔRST is an isosceles triangle. ∠R is the vertex angle. RS=x+7, ST=x-1, RT=3x-5. Find x, RS, ST, RT.

2. ΔBCD is isosceles with ∠C as the vertex angle. Find x and the measures of each side if BC=2x+4, BD=x+2 and CD=10.

3. ΔHKT is equilateral. Find x and the measure of each side if HK=x+7 and HT=4x-8.

4. ΔABC is isosceles with ∠A as the vertex angle. AC is five less than two times a number. AB is three more than the number. BC is one less than the number. Find the measure of each side.

Given ΔDAR with vertices D(2,6), A(4,-5) and R(-3,0), use the distance formula to show that ΔDAR is scalene.

Find the side lengths of equilateral ΔFGH.

Lesson Quiz

Classify each triangle by its angles and sides.

1. MNQ 2. NQP 3. MNP4. Find the side lengths of the triangle.