# What is the Cartesian form of ( 3 , ( - 15pi)/2 ) ?

Aug 16, 2017

See explanation.

#### Explanation:

$x = r \cdot \cos \varphi = 3 \cdot \cos \left(- \frac{15 \pi}{2}\right) = 3 \cdot \cos \left(\frac{15 \pi}{2}\right) =$

$= 3 \cdot \cos \left(7.5 \pi\right) = 3 \cdot \cos \left(\frac{3 \pi}{2}\right) = 3 \cdot 0 = 0$

$y = r \cdot \sin \varphi = 3 \cdot \sin \left(- \frac{15 \pi}{2}\right) = - 3 \sin \left(\frac{15 \pi}{2}\right) =$

$= - 3 \cdot \sin \left(\frac{3 \pi}{2}\right) = - 3 \cdot \left(- 1\right) = 3$

The point's coordinates are $\left(0 , 3\right)$