Find the radius 'r'(?) of the circle 'C' in the attachment.
I know AO = OB = 6cm
Where the circle touches the circumference is pi/2 (90deg).
AOC = pi/6 = (30deg).
I have no idea what to do to find r. I am unable to use the sin/cosine rules as I don't have enough information..
Can anyone give me any pointers?
Last edited by Joshmeid; 10-04-2012 at 20:19.
(Original post by TheMagicMan)
Anyway extend OC to the arc AB. Can you now determine
if I say that
. Simple trig from there
a = 6-|OC|
a = radius
OC/Sin(pi/2) = a/Sin(pi/6)
OC/Sin(pi/2) = 6 - |OC|/Sin(pi/6)
Sin(pi/6)|OC|/Sin(pi/2) = 6 - |OC|
1/2|OC| = 6 - |OC|
|OC| = 12 - 2|OC|
3|OC| = 12
|OC| = 4
a = 6 - |OC|
a = 6 - 4
a = 2
Therefore Radius = 2. Is this correct?
Last edited by Joshmeid; 11-04-2012 at 20:35.
I sat this paper, and used a reasonably complicated argument involving incircles and inversion...the examiner was undoubtedly not happy...when I saw the approved solution later I was
(Original post by raheem94)
Yes, it is.
It came in the june 2011 edexcel C2 paper, and this question cost me 100 that day
. Though its a simple question but that day the exam conditions also played its part, and i failed to find the radius.
Last edited by TheMagicMan; 10-04-2012 at 20:12.