Chapter 10 - Parametric Equations and Polar Coordinates - 10.3 Exercises - Page 687: 16

This curve corresponds to a line that is parallel to the $y$ axis, at $x = 4$.

Knowing that $rcos(\theta) = x$: $r = 4sec (\theta)$ $r = \frac{4}{cos(\theta)}$ $rcos(\theta) = 4$ $x = 4$ - This curve follows the pattern* for a vertical straight line that is parallel to the $y$ axis, but at $x = constant$, which is $4$ in this case. * $x = constant$