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Published bySuzan Griffith Modified over 9 years ago
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What did you do yesterday? Can I turn a circle into a rectangle?
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Too bumpy on the top and bottom! Hmm, odd number of pieces... trapezoid. 12 pieces and I have a parallelogram, not so bumpy across the top and bottom.
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The more sectors, the more the shape looks like a rectangle/parallelogram. What did you find out? rect·an·gle : a four-sided shape that is made up of two pairs of parallel lines and that has four right angles; especially : a shape in which one pair of lines is longer than the other pair par·al·lel·o·gram : a four-sided shape made up of two pairs of straight parallel lines that are equal in length : a quadrilateral with opposite sides parallel and equal
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What does the base of the parallelogram have in common with the circle?
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The base is about one- half the circumference of the circle 1 1 2 2 3 3 4 4 5 5 6 6 In my picture, you can see that the bottom or base of the parallelogram is the same as half of the circumference of the red circle. I drew the sectors onto the shapes to show that the edges of the sectors make the base and the circumference.
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What does the height of the parallelogram have in common with the circle? height
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1 1 2 2 3 3 4 4 5 5 6 6 In my picture, you can see that the sides of the parallelogram are about the same length as a side of a sector. The height of the parallelogram is about the radius of the circle. 7 7 I say “about” because the sides of the sectors are a bit shorter than the distance from the vertex of the sector to its outside edge.
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On your own/with a partner, decide which parallelogram best represents the area of the circle. Justify your answer using evidence! What could you do to get a better estimate for the area?
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What happens to the height and radius when the number of congruent/equal sectors increases? (What happens when you use more equal sectors?) As you use more pieces, the height and radius become closer in value.
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