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Equations of circles
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November 5, 2018
Aug 215:12 PM
L.O. To be able to find the equation of a circle 05/11/18Starter
Complete the square for the following:
a) x2 + 10x 4
b) x2 5x + 2
c) x2 + 6x
d) x2 19x
Aug 215:12 PM
L.O. To be able to find the equation of a circle 05/11/18Example
A circle has centre (0, 0) and a radius of 13. Does the following points lie inside the circle, outside of the circle or on the circumference of the circle?
a) (12, 5)
b) (9, 9)
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Equations of circles
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November 5, 2018
Aug 215:12 PM
L.O. To be able to find the equation of a circle 05/11/18
You should know from GCSE that the equation of a circle with centre (0, 0) and radius r, is:
x 2 + y 2 = r 2
Example
A circle with centre (0, 0) and radius 5, is translated by the vector .
Find the equation of the circle after the translation.
Aug 215:12 PM
L.O. To be able to find the equation of a circle 05/11/18
The equation of a circle with centre (a, b) and radius r, is:
(x a) 2 + (y b) 2 = r 2
Quick questions
Write down the equation of the circles with:
a) Centre (5, 6) and radius 4
b) Centre (2, 3) and radius √7
c) Centre (5, 11) and radius 2π
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Equations of circles
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November 5, 2018
Aug 215:12 PM
L.O. To be able to find the equation of a circle 05/11/18Example
Write the equation of the circle x2 2x + y2 + 4y + 1 = 0 in the form (x a)2 + (y b)2 = r2
Aug 215:12 PM
L.O. To be able to find the equation of a circle 05/11/18Example
Find the equation of the circle that has a line segment from (7, 1) to (1, 3) as the diameter.
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Equations of circles
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November 5, 2018
Nov 508:41
Nov 508:41
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