$\"\"$

The differential equation is $\"\\frac{dr}{d\\theta$ .

$\"dr=\\pi$

Apply integral on each side.

$\"\\int$

Apply Integration formula $\"\\int$ .

$\"r=\\pi$ .

$\"\"$

Check the solution by using differentiation.

$\"r=\\pi$

Apply derivative on each side with respect to $\"\\theta\"$ .

$\"\\frac{d}{d\\theta$

$\"\\frac{dr}{d\\theta$

$\"=\\frac{d}{d\\theta$

$\"=\\pi$

$\"=\\pi(1)\"$

$\"\\frac{dr}{d\\theta$ .

$\"\"$

The general solution of differential eqation is $\"r=\\pi$ .