Download 4-2-properties-of-triangles-acute-obtuse-right

Geometry/Trig
Name: ______________________________
Date: _______________________________
Lesson 4-2 Properties of Triangles
Learning Goals: (4) What is the sum of all of the interior angles in a triangle? (5) How do you classify
the different types of triangles by angles? (6) How do you classify the different types of triangles by sides?
Warm Up
*use your notes from yesterday to
guide your thinking!
1. Name the indicated angle in two different ways:
2. Name the angle relationship shown:
______________ Angles
_______________ Angles
____________ Angles
3. Using the picture below, determine the measure of each angle that’s listed.
_______________
Geometry/Trig
Discover it!
Angles of a Triangle
What do you notice about all three angles in ∆ABC?
The sum of the interior angles in a triangle
is _____________.
Apply it!
1. What is the measure of ∠𝐶?
2. In ∆ABC, m∠A = 42° and m∠C = 63°. What is the measure of ∠B?
3. In ∆ABC, m∠A = x° and m∠B = 2x+2° and m∠C = 3x+4°, what is the value of x?
Geometry/Trig
Discover it! Classifying Triangles by their Interior
Angles
Apply it!
Classify the following triangle using angles :
4. The angles of a triangle are in a 350, 510, and 1230. Is the triangle acute, obtuse, or right? Justify your answer.
Remember!
“Justify” means
to write out your
thinking!
Discover it! Classifying by Sides:
A triangle will always have either:
No Congruent Sides
2 (one pair) Congruent Sides:
Geometry/Trig
3 (all) Congruent Sides:
Apply it!
5. The sides of a triangular garden are in a 150 inches, 160 inches, and 175 inches. Is the garden an isosceles,
scalene, or right triangle? Justify your answer.
6. Classify all of the following triangles according to its sides.
This triangle isa ______________
triangle because
 it has
_____________________________

This triangle is a ______________
triangle because it has
_____________________________
This triangle is a ______________
triangle because it has
_____________________________
This triangle is a ______________
triangle because it has
_____________________________
Now, Master It!
7. In ∆ABC, m∠A = 2x° and m∠B = 2x+2° and m∠C = 3x+4°, what is the value of x to the nearest tenth of a
degree?
Geometry/Trig
8. The angles of a triangle a given triangle are: 1010, 510, and 280. Is this triangle acute, obtuse or right?
Fill in the blanks: According to its angles, triangle is _____________________, because it contains
_________________________________________________________________.
9. Classify the following triangle by its angles. (Acute, obtuse, or right).
This triangle is ___________________ because it contains_____________________________________.
10. Given Triangle ABC, 𝑚∡A = 30°, 𝑚∡B = 2x°, 𝑚∡C = 70°
a. find the measurement of angle B.
b. Is triangle ABC acute, obtuse, or right?
c. Triangle ABC is __________________________ because _____________________________________________
__________________________________________________________________.
11. Classify the following triangles by their sides:
a)
b)