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DRILL (A) Name the cross-sections you would find in a cone, cylinder, cube, rectangular prism. (B) What solids would you use to model these farm structures? Why would we want to know?. What would you get if you turned these shapes about their axes?. Rotating Triangle in 3D.
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DRILL (A) Name the cross-sections you would find in a cone, cylinder, cube, rectangular prism. (B) What solids would you use to model these farm structures? Why would we want to know?
What would you get if you turned these shapes about their axes?
Rotating Triangle in 3D Axis bisects triangle Rotation creates a cone
Triangle: Axis Along Edge Edge along axis forms center axis of solid Other edges create curved surfaces
Rectangle: Axis Bisecting Edges perpendicular to axis draw flat faces Edges parallel to axis draw curved surfaces Rotation creates: cylinder
Rectangle: Axis Along Edge Edges perpendicular to axis draw flat faces Edges parallel to axis draw curved surfaces Rotation creates: cylinder
Circle: Axis Bisecting Curved edges draw curved surfaces Rotation creates: sphere
Circle: Axis Along Edge Curved edges draw curved surfaces Rotation creates: torus
Why does V = B x h calculate the volume of prisms & cylinders? How do you know you can trust the formulas? h V = B x h B
Cavalieri Principle If cross-sectional area of two prisms is the same for every height above the base, then the volumes will be the same. Bonaventura Cavalieri
Cylinder: US Quarter h = .7in B = 2.86in2
Stack of 16 quarters V = 2.86 x11.2=32 in3 B = 2.86in2 h = 11.2 in
Works for unusual shapes If base area is congruent, multiply B x h to easily calculate volume. height