How to Make a Cone Shape
A cone shape can be made out of paper or poster board by tracing out a circle with a compass. The strategy is to cut a wedge out of the circle, and then join the two edges of the wedge (or the remaining circle) together. The wedge point will be at the center of the circle. The angle of the wedge determines how high the cone will be. By adjusting this angle, you can select the cone height.
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Things You'll Need
- Pencil
- Compass
- Paper
- Scissors
- Ruler
- Tack and string (optional)
- Protractor
- Calculator
Instructions
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1
Mark on the paper or poster board where the center of the circle is to be.
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Draw a circle using a compass, placing the sharp end at the center of the circle and tracing out the circle with the pencil end. An alternative is to tack one end of string at the circle center and tie a pencil to the other end. The string and compass keep the circle of equal radius all the way around.
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3
Cut out the traced circle with scissors.
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Draw one straight line from the edge to the marked center with the ruler.
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5
Decide how tall you want the cone to be. The height will have to be less than the radius of the circle.
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Plug the desired height into the formula d/360 = √[1-(h/R)^2], where h is the height you want the cone to be, R is the radius of the circle, √ signifies the square root of the quantity in brackets, and d is the number of degrees spanned by the portion of the circle that you'll make into a cone.
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Place the eye of the protractor at the center of the circle and the baseline of the protractor over the line you just drew. Find 'd' degrees on the protractor and put a mark next to the angle. (If 'd' is greater than 180 degrees, just subtract it from 360 and find that angle on the protractor instead.)
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Draw a line from the circle center through the mark you just made and extend it to the edge of the circle. Use the ruler again to trace the line straight.
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9
Cut along the two straight lines to cut out a triangular wedge.
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Join the two edges created by cutting out the wedge for the portion of the circle that you want to make into a cone. This turns the two-dimensional circle into a three-dimensional cone. The two corners left over will just touch each other when the two edges are joined. You now have your cone.
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Paste some extra paper on the inside of the seam made by the two edges. This will keep the cone from unfolding.
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Tips & Warnings
Your cone should sit flat on its circular edge, because the distance from the cone tip to the edge is equal all the way around and because any line drawn from the cone tip to the edge is perpendicular to the edge. These properties come from your making the original circle the same radius all the way around. Such a shape is called a "right cone."
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Comments
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or you could just cut a circle in half
