# Tangents of polar curves

### Tangents of polar curves

In this lesson, we will learn how to find the tangent line of polar curves. Just like how we can find the tangent of Cartesian and parametric equations, we can do the same for polar equations. First, we will examine a generalized formula to taking the derivative, and apply it to finding tangents. Then we will look at a few examples to finding the first derivative. Lastly, we will do some applications which involve finding tangent lines of polar curves at a specified point.

#### Lessons

In order to find the tangent line to polar curves, we have to take the derivative in polar coordinates.
Here is the formula to take the derivative in polar coordinates:
$\frac{dy}{dx}=\frac{\frac{dr}{d \theta}\sin \theta+r\;\cos \theta}{\frac{dr}{d \theta}\cos \theta-r\;\sin \theta}$
• Introduction
Tangents of Polar Curves Overview

• 1.
Finding the Derivative
Find $\frac{dy}{dx}$ for each of the following polar equations:
a)
$r=\sin \theta + \theta$

b)
$r= \frac{\sin \theta}{\cos \theta}$

• 2.
Finding the Tangent Line
Find the tangent line with the following polar curves at the specified point:
$r=\sin (3\theta)$ at $\theta = \frac{\pi}{4}$

• 3.
Finding the Tangent Line
Find the tangent line with the following polar curves at the specified point:
$r=\theta \cos \theta$ at $\theta =0$