Homework 4.1 – Triangle Sum & Classifying Triangles
Name: __________________________
Block: _______
Date: ___________
Complete the sentence with always, sometimes, or never.
1. An isosceles triangle is ____________________ a right triangle.
2. An obtuse triangle is ____________________ a right triangle.
3. A right triangle is ____________________ an equilateral triangle.
4. A right triangle is ____________________ an isosceles triangle.
Find the value of x. Then classify the
triangle by its angles.
5.
6.
x=
Triangle: ___________
x=
7. A triangle has the given vertices.
Graph the triangle and classify it by its sides.
Then determine if it is a right triangle.
AB = _______ BC = _______ AC = _______
slope AB = ____ slope BC = ____ slope AC = ____
Therefore
ABC is a _______________ triangle
and IS / ISN’T a right triangle.
Triangle: _________
A (3, 3), B (6, 9) , C (6, -3)
8. Find the measure of the exterior angle.
#9-14 Find the measure of the
numbered angle.
9. m  1=
12. m  2 =
10. m  3 =
13. m  4 =
11. m  5 =
14. m  6 =
15. PROVE: Exterior Angle Theorem
Given:  1 is an exterior angle of  ABC
1
Prove: m  1 = m  A + m  B
Statements
1.  1 is an exterior angle
Reasons
1. Given
2.  ACB and  1 are a linear pair
2.
3.
3. Linear Pair Postulate
4. m  ACB + m  1 = 180°
4.
5. m  A + m  B + m  C = 180°
5.
6. m  ACB + m  1 = m  A + m  B + m  C 6.
7. m  ACB = m  C
7.
8. m  ACB + m  1 = m  A + m  B + m  ACB
8.
9.
9.
Find the measure of each angle.
16. In ABC, mA = mB + 30° and mC = mB + 60°. Find the measure of each angle.
17. In ABC, mA = 2(mB) and mC = 3(mB). Find the measure of each angle.
Find the values of x and y.
18.
Hint: what
special pair
of angles is
formed by
the parallel
lines?
19.
20.