Solve dθ+Ndr=0

$$d \theta + N d r = 0$$

Solve for N

$$\left\{\begin{matrix}N=-\frac{\theta }{r}\text{, }&r\neq 0\\N\in \mathrm{R}\text{, }&d=0\text{ or }\left(\theta =0\text{ and }r=0\right)\end{matrix}\right.$$

Steps for Solving Linear Equation

Subtract d\theta from both sides. Anything subtracted from zero gives its negation.

$$Ndr=-d\theta$$

The equation is in standard form.

$$drN=-d\theta$$

Divide both sides by dr.

$$\frac{drN}{dr}=-\frac{d\theta }{dr}$$

Dividing by dr undoes the multiplication by dr.

$$N=-\frac{d\theta }{dr}$$

Divide -d\theta by dr.

$$N=-\frac{\theta }{r}$$

Solve for d

$$\left\{\begin{matrix}\\d=0\text{, }&\text{unconditionally}\\d\in \mathrm{R}\text{, }&\theta =-Nr\end{matrix}\right.$$

Steps for Solving Linear Equation

Combine all terms containing d.

$$\left(\theta +Nr\right)d=0$$

The equation is in standard form.

$$\left(Nr+\theta \right)d=0$$

Divide 0 by \theta +Nr.

$$d=0$$