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# Coordinate Geometry of circles watch

1. A circle with centre C has equation x^2 + y^2 +8x - 12y = 12
11 (a)
Find the coordinates of C and the radius of the circle.

i got 8 for radius and (-4,6) for C

11 (b)
The points P and Q lie on the circle.
The origin is the midpoint of the chord PQ.
Show that PQ has length n√3 , where n is an integer.

im stuck on how to answer part B
drew out the circle on the graph but im still stuck
2. (Original post by Chez 01)
...
If the centre is R, then the segment RO is a perpendicular bisector to PQ. Furthermore, you can actually find the length of the segment RO. Also you know that the length of the segment RP is the radius. Note the right-angled triangle ROP and deduce the length of PO
3. (Original post by RDKGames)
If the centre is R, then the segment RO is a perpendicular bisector to PQ. Furthermore, you can actually find the length of the segment RO. Also you know that the length of the segment RP is the radius. Note the right-angled triangle ROP and deduce the length of PO
i dont understand
4. (Original post by Chez 01)
i dont understand
You can find the lengths of the purple and black dashed lines, hence determine half of the orange one through Pythagoras.

5. thank you for the graph, i drew my circle graph wrong. l will attempt the question again

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Updated: January 21, 2018
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