Q. 51 - Calculus

Question

Use polar coordinates to graph the conics in Exercises 44–51. 

$r=\frac{2}{2+\sin \theta }$

Step-by-Step Solution

Answer

The graph is 

Step 1. Given information.

The given equation is $r=\frac{2}{2+\sin \theta }$.

Step 2. Comparison.

On comparing the given equation with standard form $r=\frac{eu}{1+e\sin \theta }$.

$$\begin{gathered} r=\frac{\frac{2}{2}}{\frac{2+\sin \theta }{2}} \\ r=\frac{1}{1+\frac{1}{2}\sin \theta } \\ \text{ Here }eu=1 \\ \text{ The eccentricity }e=\frac{1}{2} \\ u=2 \end{gathered}$$

Step 3. Graph.

For $r=\frac{2}{2+\sin \theta }$the eccentricity is $e=\frac{1}{2}$, so the graph is an ellipse. The directrix is parallel to the polar axis at a distance $u=2$ units above the pole. The directrix is $2$ units above the pole .