Let be the solution of the differential equation , , and let . Then the number of integral values of , for which the equation represents a circle of radius , is ______.
$\sin\!\left(\frac{y}{x}\right)\frac{dy}{dx} = \frac{y}{x}\sin\!\left(\frac{y}{x}\right)-1$
put $y=tx \Rightarrow \frac{dy}{dx} = t+x\frac{dt}{dx}$
$\sin t\left(t+x\frac{dt}{dx}\right) = t\sin t-1$
$\Rightarrow -\cos t+\ln x=C$
$\Rightarrow -\cos\!\left(\frac{y}{x}\right)+\ln x=C$
$y(1)=\frac{\pi}{2} \Rightarrow C=0$
$\Rightarrow \cos\!\left(\frac{y}{x}\right)=\ln x$
$\csc\!\left( \frac{y(e^{12})}{e^{12}} \right) = 12 \Rightarrow \alpha=12$
$\Rightarrow r\le 6 \Rightarrow r^2\le 36$
number of integral value of
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