Paper 2 · Co-ordinate Geometry of the Circle
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Lesson 1 of 9
The Circle 1 – Introduction
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- Write a circle's equation from centre and radius: (x−h)² + (y−k)² = r²
- Extract centre (−g, −f) and radius √(g²+f²−c) from x²+y²+2gx+2fy+c = 0
- Rearrange the equation to '= 0' before reading off 2g, 2f and c
- Substitute g and f (not −g, −f) into the radius formula for full marks
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