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coordinate geocircle
by anachu17 Leaving Cert Mathematics — 10/05/16 5

if the length of the tangent from Q (2,-1)to the point of contact P to the circle s: x(squared)+ y(squared)-2x-4y+k= 0 is 5, find k i dont know what to do !i havethe centre which is 2,-1 and the distance from centre to q ( square root of 10)


5 Comments
AHickey — 10/05/16
The centre is (1,2) as in (-g,-f) . Draw a rough diagram. You have a right angled triangle. Point Q is not on the circle ,it is just a point on the tangent. P is the point of contact of the circle and the tangent and it is where the right angle is. The radius ( the square root of g squared + f squared -c), you can work out but if will be in terms of k. Also get the distance from Q to the centre ( this is the hypotenuse of the triangle). Use Pythagorus Theorem on the 3 sides( the 3rd side being 5) and the only unknown is k.( c in the radius formula is k)
JackW — 10/05/16
What year is this
fionnanros — 10/05/16
if u liked it then u shud of but a ring on it
anachu17 — 10/05/16
thank you so much
anachu17 — 10/05/16
jack w it was in a worksheet
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