# What is the graph of # r = a ± a cos θ#?

##### 1 Answer

Aug 14, 2018

A cardioid

#### Explanation:

This is a cardioid.

We can observe that the positive/negative just flip the orientation of the figure since cosine goes from -1 to 1 either way. Let's just discuss the negative case for now, but remember that it doesn't really matter (it just rotates it by an angle of 180 degrees)

We observe that there is an angle where the value goes all the way to 0 (

graph{ sqrt(x^2+y^2) = x^2 + y^2 + x [-4, 1, -1.5, 1.5]}