Lesson 1.5: Angle Measurement
We measure a line segment’s length with a ruler. Angles are measured with something called a protractor . A protractor is a measuring device that measures how “open” an angle is. Angles are measured in degrees, and labeled with a symbol.
The Angle Addition Postulate states that if is on the interior of , then . See the picture below.
Ticket In/Ticket Out Activity:
What is the measure of the angle shown below?
What is in the diagram below?
Draw a angle.
A protractor is a measuring device that measures how “open” an angle is. Angles are measured in degrees , and labeled with a symbol. A compass is a tool used to draw circles and arcs.
Warm-Up Activity/Guided Practice:
1. Use a protractor to measure below.
2. What is if and ?
3. If , find and and ?
1. What is if and ?
2. If , find .
For questions 3-6, determine if the statement is true or false.
- For an angle is the vertex.
- For an angle and are the sides.
- The in front of means measure.
- The Angle Addition Postulate says that an angle is equal to the sum of the smaller angles around it.
For 7-12, draw the angle with the given degree, using a protractor and a ruler.
For 13-16, use a protractor to determine the measure of each angle.
Solve for .