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Visit Mrs. Cooper's 4th Grade Classroom

Lesson:  Measuring Angles
4th Grade

Standard: Measurement and Data (4.MD.C.6)
Measure angles in whole-number degrees using a protractor. Sketch angles of specified measure.

Essential Questions:

What is an angle? What geometric concepts make up an angle? How are angles used in the real world? What are the types of angles we have learned about? (right, acute, obtuse, straight)


Acute Angle:  An angle whose measure is between 0-89 degrees.
Obtuse Angle:  An angle whose measure is between 91-179 degrees.
Straight Angle:  An angle whose measure is exactly 180 degrees.
Right Angle:  An angle whose measure is exactly 90 degrees.
Protractor:  An instrumental used to measure geometric angles.
Measurement:  The exact degree or size of something.
Vertex:  The origin in which two rays meet.

Lesson Description

The main objective of this lesson was to introduce students to the concept of using a protractor to determine the measurement of an angle. Students began by reviewing the geometric concepts that make up an angle (two rays that meet at one vertex). Students then examined the different types of angles we have learned about (straight, right, acute, and obtuse) and the characteristics of each angle. After discussing the real-world connection to angles such as Architecture, Clothing Design and music we dove into the heart of the lesson.

Students are "tracking" the speaker as their peers are explaining how we use angles in our everyday lives.
Students listened to an angle song to the beat of YMCA tune.  “Right angle its 90 degrees, I said acute angle less than 90 degrees, I said obtuse angle greater than 90 degrees and a straight an-gle 180…dun dun dun dun dun...The angles are right, acute, obtuse.”  
After reviewing parts of the protractor, Jermonte identified the vertex to ensure the protractor is lined up properly in order to measure the angle accurately.
Using our class Smartboard, we examined the parts of a protractor together. Students are observing how I am manipulating the protractor on the board because they understand they will be required to come up and do the same prior to using their own protractor. 
Ethan is measuring an angle on the board. He was asked to identify on which side of the protractor he needs to start, understanding that we always begin with 0 degrees when using a protractor.  
Here students could have measured angles on paper but I wanted to do something more creative and interactive. I decided to create angles with colored tape on their desks. Here I am measuring a specific angle on the desk while following these steps: 1. Approximate the measure of your angle. (This will aid in understanding what two measurements your angle will be between once you measure with a protractor) 2. Place the origin over the center point, or vertex, of the angle you want to measure. 3. Rotate the protractor to align one leg of the angle with the baseline. 4. Follow the opposite leg of the angle up to the measurements on the protractor's arc. (Students also received a copy of the steps that were reviewed.)
Students are independently measuring angles on the desk and recording them on a sheet. Students were also able to write on their desk with dry erase markers to extend the angle lines past the original angle. I like to call this “Angle Scoot” because students are moving from one desk to another. This is a great way to get students up and moving while still being productive.
Here students are recognizing that they can also use the bottom of the protractor as a ruler to extend the line in order for a more accurate measure.