1.

Two rods of lengths 2a and 2b slide along the coordinate axes such that their ends are always concyclic. Find the locus of the centre of the circle.

Answer»

P(h, k) is the centre of the circle passing through points A, B, C and D (Fig.) where AB = 2a and DC = 2b. This implies and is implied by

 PA - PC -  radius of the circle

(PA)2 = (PC)2

(AM)2 + (PM)2 = (PA)2 = (PC)= (PN)2 + (CN)2

 where M and N are the midpoints of AB and CD, respectively. From the above, we have

a2 + k2 = h2 + b2

k2 - h2 = b2 - a2

Locus of (h,k) is y2 - x2 = b2 - a2



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