(7) Lesson 7.3

1. Identify each pair of angles as complementary, supplementary, or neither.
1. 2.
3. 4. Find the value of x.
5. Tell whether the following statement is true or false. Angles are
complementary if the sum of their measures is 180°.
6. 1 and 2 are complementary angles and m1 = 57°. What is the
measure of 2?
Course 2, Lesson 7-3

2. Course 2, Lesson 7-3
ANSWERS
1. complementary
2. supplementary
3. neither
4. x = 29
5. false
6. 33˚

3. Geometry
Course 2, Lesson 7-3
HOW does geometry help us
describe real-world objects?

4. Course 2, Lesson 7-3 Common Core State Standards © Copyright 2010. National Governors Association Center for Best Practices and
Council of Chief State School Officers. All rights reserved.
Geometry
• 7.G.2 Draw (freehand, with ruler and protractor, and with
technology) geometric shapes with given conditions. Focus on
constructing triangles from three measures of angles or sides,
noticing when the conditions determine a unique triangle, more
than one triangle, or no triangle.
Mathematical Practices
1 Make sense of problems and persevere in solving them.
2 Reason abstractly and quantitatively.
3 Construct viable arguments and critique the reasoning of others.
4 Model with mathematics.

5. •To classify triangles by using angles
and sides
•To write and solve an equation to find
a missing angle measure of a triangle
Course 2, Lesson 7-3
Geometry

6. Course 2, Lesson 7-3
Geometry
• acute triangle
• right triangle
• obtuse triangle
• scalene triangle
• isosceles triangle
• equilateral triangle
• triangle
• congruent symbols

7. Course 2, Lesson 7-3
Geometry
symbol
• triangle

8. Course 2, Lesson 7-3
Geometry
all acute angles 1 right angle 1 obtuse angle
acute triangle right triangle obtuse triangle
no congruent sides at least 2 congruent sides 3 congruent sides
scalene triangle isosceles triangle equilateral triangle

9. 1
Need Another Example?
2
3
Step-by-Step Example
1. Draw a triangle with one obtuse angle and no
congruent sides. Then classify the triangle.
Connect the two segments
to form a triangle.
Draw an obtuse angle.
The two segments of the angle
should have different lengths.
The triangle is an obtuse scalene triangle.

10. Answer
Need Another Example?
Draw a triangle with three acute angles and two
congruent sides. Then classify the triangle.
Sample answer: acute isosceles

11. 1
Need Another Example?
Step-by-Step Example
2. Classify the triangle on the house by its angles and
by its sides.
The triangle has one obtuse angle and two congruent
sides. So, it is an obtuse isosceles triangle.

12. Answer
Need Another Example?
Classify the marked triangle below by its angles
and by its sides.
right scalene

13. 1
Need Another Example?
2
3
4
Step-by-Step Example
3. Find m∠Z.
The sum of the angle measures in a triangle is 180°.
m∠Z + 43° + 119° = 180° Write the equation.
m∠Z + 162° = 180° Simplify.
–162° = –162° Subtract 162° from each side.
m∠Z = 18°
So, m∠Z is 18°.

14. Answer
Need Another Example?
In triangle ABC, m∠B = 50° and m∠C = 80° .
What is m∠A?
50°

15. 1
Need Another Example?
2
3
4
Step-by-Step Example
4. The Alabama state flag
is shown. What is the
missing measure in the
triangle?
To find the missing measure, write and solve an equation.
x + 110 + 35 = 180 The sum of the measures is 180.
x + 145 = 180 Simplify.
–145 = –145 Subtract 145 from each side.
x = 35
The missing measure is 35°.

16. Answer
Need Another Example?
A state capitol building is shown below. What is
the missing measure in the diagram?
32°

17. How did what you learned
today help you answer the
Course 2, Lesson 7-4
Geometry
HOW does geometry help us
describe real-world objects?

18. How did what you learned
today help you answer the
Course 2, Lesson 7-4
Geometry
HOW does geometry help us
describe real-world objects?
Sample answers:
• To use types of triangles, such as right and acute,
when describing real-world objects
• To use angle relationships to find angle measures of
real-world, triangular shaped objects

19. Explain how classifying
angles helps to classify
a triangle as acute,
right, or obtuse.
Course 2, Lesson 7-3
Ratios and Proportional RelationshipsFunctionsGeometry