# Lesson 13

Adding the Angles in a Triangle

### Problem 1

In triangle $$ABC$$, the measure of angle $$A$$ is $$40^\circ$$.

1. Give possible measures for angles $$B$$ and $$C$$ if triangle $$ABC$$ is isosceles.
2. Give possible measures for angles $$B$$ and $$C$$ if triangle $$ABC$$ is right.

### Problem 2

For each set of angles, decide if there is a triangle whose angles have these measures in degrees:

1. 60, 60, 60
2. 90, 90, 45
3. 30, 40, 50
4. 90, 45, 45
5. 120, 30, 30

If you get stuck, consider making a line segment. Then use a protractor to measure angles with the first two angle measures.

### Problem 3

Angle $$A$$ in triangle $$ABC$$ is obtuse. Can angle $$B$$ or angle $$C$$ be obtuse? Explain your reasoning.

### Problem 4

For each pair of polygons, describe the transformation that could be applied to Polygon A to get Polygon B.

### Solution

(From Unit 1, Lesson 3.)

### Problem 5

On the grid, draw a scaled copy of quadrilateral $$ABCD$$ using a scale factor of $$\frac12$$.