## Reflection: Relevance The Parabola (Day 2 of 2) - Section 2: Where are parabola used?

I have found that students really become interested in learning about the conic sections when they see how they are used in our world.

For parabolas I am have the Mirage toy and share this with the students. In this video you can see how excited the student get when they are trying to touch the pig.  The reaction I get when the students see the toy for the first time is exciting.

During this class you hear one student saying he has one of these at home.  Another student says she is scared to touch the pig and jumps when she puts her finger on the mirage.  After each student has seen the pig. I explain how the toy works we discuss how this is 2 parabolic shapes. The real pig is at the focus of the top parabola the hologram is at the other focus.  Students will ask if this is how all holograms are made.  My answer is that I am not sure but this is one way to make the hologram.

I also bring in my personal experience with the parabola. When I was in high school my father bought a large fiberglass dish that was popular. This dish was the first ones used by companies like Dish Network and Directv. Of course the receiver is a lot smaller now.  The one my father bought did not have a receiver attached or any of the part. To make the receiver work my father researched the design and then determined where the focus of the dish would be he made parts and eventually we had a working dish. All satellite TV signals reflect off the parabola to the focus. The receiver is put at the receiver.

Another example that my students understand is a phenomena that occurs in one of our classrooms that is called the Little Theater. This room is shaped somewhat parabolic like.  If you stand at a certain spot on the floor of the room your voice is reflected back to you. Many of my students are involved in the theater program and know about this spot.  When I bring this to there attention they get really excited because they now have a logical reason why the echo occurs.

Relevance: Getting "Hands-on" with parabolas

# The Parabola (Day 2 of 2)

Unit 5: Conics
Lesson 4 of 13

## Big Idea: Why are the directrix and the focus important to understanding parabolas?

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Standards:
Subject(s):
Math, completing the square, conic sections, parabola, parabolic dish, real world applications, parabolic equations, General Form, standard form, Conics
50 minutes

### Katharine Sparks

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