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Published byMaliyah Limmer Modified over 2 years ago

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Warm-Up’s

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Warm-Up’s

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The circumference and Area of a circle

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Diameter Radius centre What is the formula relating the circumferenc e to the diameter?

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People knew that the circumference is about 3 times the diameter but they wanted to find out exactly. C = ? x d C ≈ 3 x d This means APPROXIMATELY EQUAL TO

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The exact true value is…………… UNKNOWN!!

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An approximation to π π≈ forever….

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What about the AREA of a circle? 2r r First consider a square The area of this square in terms of r is A= 2r x2r = 4r 2

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What about the AREA of a circle? 2r Now consider a circle inside the square The area of the circle must be less than the are of the square A < 4r 2 r Area = ? xr 2

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Finding a formula for the area of a circle

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C= πd or C=2πr Semi-circle=πr πrπr r

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Area of Rectangle= Base x Height Area = πr x r Area =πr 2

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The Area and Perimeter of a Circle A circle is defined by its diameter or radius Diameter radius The perimeter or circumference of a circle is the distance around the outside The area of a circle is the space inside it The ratio of π (pi) π is an irrational number whose value to 15 decimal places is π = We usually say π≈3.14 The circumference is found using the formula C=π d or C= 2πr (since d=2r) The area is found using the formula A=πr 2

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The Area and Perimeter of a Circle A circle is defined by its diameter or radius Diameter radius The perimeter or circumference of a circle is the distance around the outside The area of a circle is the space inside it The ratio of π (pi) π is an irrational number whose value to 15 decimal places is π = We usually say π≈3.14 The circumference is found using the formula C=π d or C= 2πr (since d=2r) The area is found using the formula C=πr 2

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Videos on Circles A Rap about circles Dw0&feature=related

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