| Exam Board | OCR |
|---|---|
| Module | C1 (Core Mathematics 1) |
| Marks | 4 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Circles |
| Type | Find centre and radius from equation |
| Difficulty | Moderate -0.8 This is a straightforward completing-the-square exercise for circles, requiring only algebraic manipulation to convert to standard form (x-a)²+(y-b)²=r². It's a standard C1 technique with no problem-solving element, making it easier than average, though not trivial since it requires careful algebraic execution. |
| Spec | 1.03d Circles: equation (x-a)^2+(y-b)^2=r^21.03e Complete the square: find centre and radius of circle |
3. A circle has the equation
$$x ^ { 2 } + y ^ { 2 } - 6 y - 7 = 0$$
(i) Find the coordinates of the centre of the circle.\\
(ii) Find the radius of the circle.\\
\hfill \mbox{\textit{OCR C1 Q3 [4]}}