Geometric Definitions

Contributor: Marlene Vogel. Lesson ID: 11078

What goes better with pizza than . . . math! Math? Yes, without angles and bisectors and stuff you'd have to eat an entire uncut pizza! Have fun learning and using and drawing these geometric figures!


High School

learning style
Kinesthetic, Visual
personality style
Beaver, Golden Retriever
Grade Level
High School (9-12)
Lesson Type
Dig Deeper

Lesson Plan - Get It!


Drink Stand

Congratulations! Your local amusement park has agreed to allow you to construct and operate a drink stand in their park. You are given a map of the park and told to decide on a location. Begin by accessing the Drink Stand document located in Downloadable Resources in the right-hand sidebar. Complete what you can throughout the lesson. The Drink Stand Answer Key is also located in Downloadable Resources if you get stuck. All the information you will need to complete this activity is provided in the documents.

The purpose of this lesson is to add more words to your geometry vocabulary. Below is a discussion that explains important geometry terms in depth:


The midpoint is the place that is directly in the middle of two points. Knowing where the midpoint is on any given geometric shape will help you find the middle of that shape, and can also help you figure out if the sides of the geometric shape are congruent, or equal



A bisector is something that splits a geometric figure into two equal parts. Real-life examples of how a bisector is used can be found in carpentry and sewing. The carpenter or seamstress may need to adjust the size of a shape. By using a bisector, he or she can assure the shape is cut into equal halves. There are two types of bisectors, and they are listed below:

Perpendicular Bisector

This type of bisector is used to cut a line segment into two equal halves. Because this bisector helps form two congruent geometric figures, it must go through the midpoint. One real-life example of a perpendicular bisector is an intersection of roads.


Angle Bisector

This bisector's job is to split an angle into two congruent, or equal, geometric figures. A good, real-world example of angle bisectors is the design and construction of Ferris wheels. Look at the picture below. You can see that the Ferris wheel is constructed in such a way that it has support beams placed in the shape of angles, and other support beams that are bisectors of those angles. The use of the bisectors adds to the sturdiness and safety of the ride.

Ferris wheel

Perpendicular Lines

Similar to perpendicular bisectors, perpendicular lines help split geometric figures. However, perpendicular lines do not have to go through the midpoint; therefore, they do not have to cut a geometric figure into congruent parts.

The activities in the following Got It? section will give you an opportunity to practice the skills you just learned in the section.

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