learning objectives 1.you will construct a circle using a compass. 2.you will draw the following...
TRANSCRIPT
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Learning Objectives1. You will construct a circle using a compass.
2. You will draw the following parts of a circle: center, radius, diameter, and chord.
3. You will construct a circle without using a compass.
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Developed byIvan Seneviratne
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What is a Compass?
A compass is a hinged device for drawing circles.
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Galileo's Proportional CompassThe first proportional compass was
invented in Padua in 1597. The inventor, Galileo, saw three main uses of his compass:
1. As a bomber's sight, 2. Calculation of the height of a star above
the horizon and3. Measuring the inclination of the slopes of
a wall.
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needle lead
Preparing the Compass
1. Sharpen the lead.
2. Adjust the needle and the lead so that the tip of the needle extends slightly more than the lead.
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Using the Compass
3. To draw a circle, apply enough pressure to the needle by holding the compass handle between thumb and index fingers.
4. To complete drawing the circle, revolve the handle clockwise.
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Drawing without Compass
Here's a way to draw a circle using something normally already on hand....
1.
1. Simply cut a strip of 1" wide and a little longer than the radius of the circle needed.
2. Punch a hole in one end, where the point of a pencil could be placed through for drawing.
3. Place a pin on the other end precisely the distance from the pencil hole which
represents the radius of the circle.
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Drawing without CompassTo draw a circle, stick the pin into your drawing surface,
put a pencil in the hole and rotate around the pin 360 degrees.
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World Freehand Circle Drawing Championship
2007Alexander Overwijk, a teacher from
Ottawa, Canada, is one of the fastest Circle Drawers in the world. He draws a close-to-perfect 3 foot wide circle in less than two seconds.
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Your Turn1. Draw a circle that has a radius of 4 cm
on the given origami paper.
2. Cut the circle into a semi circle and a quarter circle.
3. Paste the quarter circle and the semi circle on a Journal Writing sheet.
4. Find the perimeter of each shape.
5. Show clearly how you derived the answers.
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Images - http://apod.nasa.gov http://www.britannica.com
This presentation is developed by Ivan Seneviratne © 2007 purely for personal use.
Acknowledgments