# What is the Cartesian form of (91,(-13pi) /12)?

##### 1 Answer
Oct 18, 2017

$\left(- 87.90 , 23.55\right)$

#### Explanation:

It can be seen from the diagram that the x coordinate of P is $r \cos \left(\theta\right)$ and the y coordinate of P is $r \sin \left(\theta\right)$

So:

$x = r \cos \left(\theta\right)$

$y = r \sin \left(\theta\right)$

From example:

$\left(91 , \frac{- 13 \pi}{12}\right)$

$x = \left(91\right) \cos \left(\frac{- 13 \pi}{12}\right) = - 87.89925019 = - 87.90$ (2 .d.p.)

$y = \left(91\right) \sin \left(\frac{- 13 \pi}{12}\right) = 23.55253310 = 23.55$ (2 .d.p.)

Cartesian coordinate is:

$\left(- 87.90 , 23.55\right)$

Polar Graph: