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### Course: Get ready for AP® Calculus>Unit 7

Lesson 7: 2D vs. 3D objects

# Dilating in 3D

The cross sections of 3D shapes are dilations of the original shape, centered at a specific point. The scale factor of the dilation depends on the height of the cross-section or the distance from the point on the base.  Created by Sal Khan.

## Want to join the conversation?

• Would the dilations and cross sections look the same if you put the 3D pyramid on a coordinate plane?
• How can you put a 3D object such as a pyramid on a coordinate plane which is 2 dimensional? You could put it within a 3D space on an x-y-z coordinate system, but not a coordinate plane.
• Would it look the same if it was a 3D pyramid?
• I'm sorry, but a pyramid is always 3D, so your question makes no sense.
• im falling asleep
• So dont!
You must pay attention if you're going to learn anything from Sal!
• why does it keep asking for more questions
• هل يمكن لأي شخص أن يشرح لي هذا في فترة أسبوعين
• Would the dilations and cross sections look the same if you put the 3D pyramid on a coordinate plane
(1 vote)
• One, you copied @FemiO, two you can't put a 3D object on a coordinate plane.
• How do we know which dilation is a 0.5 or a 0.75?
• Think of the 0.5 dilation being the halfway point between points B and P going down. For the 0.75 dilation you use the same method, but you go further down (obviously). The closer you cut to the base of the pyramid, the bigger the dilation fraction is.
(1 vote)
• Would the dilations and cross sections look the same if you put the 3D pyramid on a coordinate plane?