1. 02.19.2018 Agenda Bell Ringer Bell ringer
Introduction Video-Cross Sections m/watch?v=hlD_j3AtxGs
Cornell Notes
Topic-Cross Sections
E.Q. How do I determine the Cross section of a given shape?

2. Bell Ringer Answer
(8/2)*(9-3) = 24 
(9-2*3)*8 = 24

3. Cross Sections of Three-Dimensional Figures
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4. 3-Dimensional figures can be cut by planes
3-Dimensional figures can be cut by planes. When you cut a 3-D figure by a plane, the result is a 2-D figure.
The cross-sections of 3-D figures are 2 dimensional figures you are familiar with.
Look at the example on the next page to help your understanding.

5. Vocabulary
A polyhedron is a three-dimensional solid with flat surfaces and straight edges.
Each polygon is a face of the polyhedron.
An edge is a segment that is formed by the intersection of two faces.
A vertex is a point where three or more edges intersect.
A net is a two-dimensional pattern that you can fold to form a three-dimensional figure.
One of the simplest such figures is a cube — a polyhedron with six faces, each of which is a square.

6. Vocabulary
Prisms: polyhedron with 2 congruent and parallel faces called bases.
Pyramid: polyhedron in which 1 face is a polygon and the others are triangles…comes to a point at the top.
Cylinder: 3D figure with 2 congruent & parallel bases that are circles
Cone: has 1 circular base and comes to a point at top

7. Cross Sections
A cross section is the shape formed when a plane intersects a 3D figure.
Think of a very thin slice of the solid.
The bases are opposite faces that are parallel and congruent.
To describe the relationship between the plane and the solid, it will be either:
Parallel to the base or
Perpendicular to the base
Cross-Sections can be polygons and circles
Tell the shape it makes when you cut the solid

8. A horizontal cross-section of a cone is a circle.
Can you describe a vertical cross-section of a cone?

9. A vertical cross-section of a cone is a triangle.

10. A water tower is built in the shape of a cylinder.
How does the horizontal cross-section compare to the vertical cross-section?

11. The horizontal cross-section is a circle.
The vertical cross-section is a rectangle

12. Which figure has the same horizontal and vertical cross-sections?9
Which figure has the same horizontal and vertical cross-sections? A C B D
Answer: C

13. Which figure does not have a triangle as one of its cross-sections?10
Which figure does not have a triangle as one of its cross-sections? A C B D
Answer: C

14. Which is the vertical cross-section of the figure shown?11
Which is the vertical cross-section of the figure shown? A
Triangle B
Circle C
Square
Answer: C D
Trapezoid

15. Which is the horizontal cross-section of the figure shown?12
Which is the horizontal cross-section of the figure shown? A
Triangle B
Circle C
Square
Answer: C D
Trapezoid

16. Which is the vertical cross-section of the figure shown?13
Which is the vertical cross-section of the figure shown? A
Triangle B
Circle C
Square
Answer: A D
Trapezoid

17. Reference
Sectionsof3DFigures_12_4_2013_9_46_10_AM.ppt
content/uploads/.../2a.-Notes-Nets-and-Cross- Sections.ppt