The equation of a circle in the first quadrant with centre(a,a) and radius (a)which touches the coordinate axes is:
(x-a)2+(y-a)2=a2...(1)
Differentiating equation(1)with respect to x,we get:
\(2(x-α)+2(y-α)\frac{dy}{dx}=0\)
⇒(x-α)+(y-α)y=0
⇒x-α+yy-αy=0
⇒x+yy-α(1+y)=0
\(⇒α=\frac{x+yy}{1+y}\)
Substituting the value of a in equation(1),we get:
\([x-(\frac{x+yy}{1+y})]^2+[y-(\frac{x+yy}{1+y})]^2=(\frac{x+yy}{1+y})^2\)
\(⇒[(\frac{x-y)y}{(1+y}]^2+[\frac{y-x}{1+y}]^2=[\frac{x+yy}{1+y'}]^2\)
\(⇒(x-y)^2.y^2+(x-y)^2=(x+yy)^2\)
\(⇒(x-y)^2[1+(y)^2]=(x+yy)^2\)
Hence,the required differential equation of the family of circles is
⇒(x-y)^2[1+(y)^2]=(x+yy)^2
A compound (A) with molecular formula $C_4H_9I$ which is a primary alkyl halide, reacts with alcoholic KOH to give compound (B). Compound (B) reacts with HI to give (C) which is an isomer of (A). When (A) reacts with Na metal in the presence of dry ether, it gives a compound (D), C8H18, which is different from the compound formed when n-butyl iodide reacts with sodium. Write the structures of A, (B), (C) and (D) when (A) reacts with alcoholic KOH.