Variable chord of hyperbola If a variable chord of hyperbola $x^2$$/4$ - $y^2$$/8$ $=$ $1$ subtends a right angle at the centre of hyperbola . If the chord touches a fixed concentric circle with hyperbola then we have to find the radius of the circle . 
I thought of doing it by homozenizing , but not able to do how ?

Homogenise it and then
coeff.[x^2+y^2]=0 you will get constant term and since it is tangent to the circle x^2+y^2=r^2 then equate and u will get it. 
