Point of contact of two circles
Posted 26 January 2006 - 06:45 PM
Circle A has equation x2 + y2 - 10x - 12y + 36 =0. Circle B has equation x2 + y2 + 8x + 12y -48 = 0.
(a) Find the circle and radius of each circle
(b) Show that the circles touch externally
( c) Find the point of coordinates of the point of contact of the circles
I can do (a) and (b) BUT © is just impossible. Thought it would be better to put the whole question up.
Help Please, thanks trace x x
Posted 26 January 2006 - 06:56 PM
I'm pretty sure you cover this in the Vectors outcome of Unit 3, but I can try explaining it to you if you like.
Edit: In fact, I don't think you know enough yet for me to explain it. I could be wrong but I don't see another way of doing it. You should cover it in Unit 3 though.
Posted 26 January 2006 - 07:01 PM
Thanks x x x
Posted 26 January 2006 - 07:19 PM
Remember from Vectors that you can find a point which divides a line in a ratio. That's all that's happening here.
Does this ring any bells? (You might have used the Section Formula also).
I'll go further if you still don't get it .
Posted 26 January 2006 - 07:26 PM
Posted 26 January 2006 - 07:28 PM
Posted 27 January 2006 - 07:28 AM
Centre A = (5,6) Radius A = 5
Centre B= (-4,-6) Radius B = 10
Draw a sketch (see Steves) and simply use similar triangles, one with hyp = 15 and the other hyp = 10. It is then easy to work out the p.o.c. (2,2).
Posted 28 January 2006 - 12:50 AM
Posted 28 January 2006 - 01:04 AM
i dont think that would work but in saying that it is 1am!!....would it work?
anyway, i would use duncads method
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