PROTRACTOR
Definition Of Protractor
Protractor is a tool used to measure the angles.
More About Protractor
Some of the protractors are half circle protractors to measure angles up to 180° and some of them are full circle protractors to measure angles up to 360°.
Video Examples: How to use a protractor
Example of Protractor
Solved Example on Protractor
Ques: Find the measure of ∠XYZ.
Choices:
A. 105°
B. 75°
C. 180°
D. 130°
Correct Answer: A
Solution:
Step 1: ∠XYZ is made up of two rays, YX and YZ, with the common endpoint Y.
Step 2: ∠XYZ is the measure between YX and YZ.
Step 3: On the protractor scale, YX is passing through 180° and YZ is passing through 75°.
Step 4: Difference = 180° - 75° = 105°
Step 5: The measure of ∠XYZ is 105°.
Quick Summary
- A protractor measures angles.
- Protractors can be half-circle (180°) or full-circle (360°).
- Angles are measured in degrees.
⚠️ Common Mistakes
- Reading the wrong scale on the protractor (inner vs. outer).
- Not aligning the protractor's base line with one of the angle's rays.
- Incorrectly subtracting to find the angle measure.
🌍 Real-World Uses
- Navigation: Used by sailors and pilots to plot courses on nautical charts.
- Construction: Used to measure and mark angles for building structures like roofs and walls.
- Drafting and Design: Architects and engineers use protractors to create accurate blueprints and technical drawings.
📋 Standards Alignment
CCSS.MATH.CONTENT.4.MD.C.6CCSS.MATH.CONTENT.7.G.A.2
🔗 Related Links
🍎 Teacher Insights
Emphasize the importance of accurate alignment. Use real-world examples of angles. Provide ample practice opportunities.🎓 Prerequisites
- Basic arithmetic
- Understanding of angles (acute, obtuse, right)
Check Your Knowledge
Q1: What is the measure of angle XYZ if ray YX is at 180° and ray YZ is at 75°?
Q2: A protractor is used to measure what?
Frequently Asked Questions
Q: What is the unit of measurement for angles using a protractor?
A: Degrees (°).
Q: How do I align the protractor to measure an angle?
A: Place the protractor's center point on the angle's vertex and align the base line (0° line) with one of the angle's rays.