Download 05 Angles in Triangles - ASU Modeling Instruction

Name: ________________________
Date: ___________________
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Hr: ____________
Angles in a Triangle
Part I: Angle Sums
1. Measure the angles in each triangle
below. Place your measurements in
the table. Then, for each triangle,
find the sum of the three measures.
Triangle
1
2
3
4
A
B
C
2. What is the pattern? The three angles in a triangle always add up to ___________.
3. Use your protractor to draw a triangle
(ΔABC) with A = 60° and B = 20° in the
space at right.
(a) Use reasoning: What do you THINK the
measure of C should be? ________
(b) Now measure C. How close was your
prediction?
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Sum
4. Use your protractor to draw a triangle
(ΔDEF) with D = 45° and E = 55° in the
space at right.
(a) Use reasoning: What do you THINK the
measure of F should be? ________
(b) Now measure F. How close was your
prediction?
Part II: Classifying Triangles
5. Triangles can be classified by their side lengths or by their angles. Write a brief definition
of each of the following types of triangles. Then draw a sample picture of each.
By Side Length:
(a) Scalene Triangle
By Angle:
(d) Right Triangle
(b) Isosceles Triangle
(e) Obtuse Triangle
(c) Equilateral Triangle
(f) Acute Triangle
6. Identify each of the following triangles as scalene, isosceles, or equilateral. Then identify
them as right, obtuse, or acute.
a.
b.
c.
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d.
e. Draw an isosceles right
triangle.
f. Draw an obtuse scalene
triangle.
____________________
____________________
7. A triangle with no sides congruent is a(n) _____________________ triangle.
8. A triangle with all sides congruent is a(n) _____________________ triangle.
9. A triangle with at least two sides congruent is a(n) ______________ triangle.
10. A triangle with a 90 angle is a(n) _________________________ triangle.
11. A triangle with two 40 angles is a(n) ________________________ triangle.
12. A triangle with three equal sides is a(n) _____________________ triangle.
13. A triangle with 40, 60, 80 angles is a(n) _____________________ triangle.
14. Is it possible for an triangle to have TWO obtuse angles? Why or why not?
15. Is it possible for a right triangle to have an obtuse angle? Why or why not?
16. Fill in the blanks with the appropriate number: A triangle can have AT MOST
_________ obtuse angle(s). A triangle can have AT MOST _________ acute angle(s).
A triangle can have AT MOST __________ right angle(s).
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