Page 124 - Math Course 2 (Book 2)

Classifying Triangles

m∠D + m∠E + m∠F + = 180 Your Turn!
100 + 33 + x = 180
Find Angle Measures
133 + x = 180
133 – 133 + x = 180 – 133 Find the value of x in ΔMNO.
x = 47
A. 57
x is 47 and the measure of ∠F B. 123
Answer C. 139
is 47°.
D. 303

Use Ratios to Find Angle Measures

Example

Answer
ALGEBRA
The measures of the angles of a certain triangle
are in the ratio 2:3:5. What are the measures of the
angles?

Words The sum of the measures is 180°.
Use Ratios to Find Angle Measures

Variable Let 2x represent the measure of the ALGEBRA The measures of the angles of a certain
first angle, 3x the measure of the triangle are in the ratio 3:5:7. What are the
second angle, and 5x the measure measures of the angles?
of the third angle.
A. 12°, 60°, 84°
Equation The sum of the B. 30°, 50°, 70°
2x + 3x + 5x = 180 measures is 180. C. 36°, 60°, 84°

Combine like D. 40°, 60°, 80°
10x = 180
terms. Answer
10x = 180 Divide each side
10 10 by 10.
x = 18 Simplify.

Since x = 18, 2x = 2(18) or 36, 3x = 3(18) or 54,
and 5x = 5(18) or 90.

The measures of the angles are
Answer
36°, 54°, and 90°.

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