Question

What is the Cartesian form of `( 13 , (-9pi)/4 )`?

Answer 1

First, find the coterminal angle for `(-9pi)/4`

Explanation:

coterminal angle `=4pi-(9pi)/4=(7pi)/4`

`(7pi)/4` is in quadrant IV , so x is positive and y is negative .

`x=13cos((7pi)/4)=13sqrt2/2`

`y=13sin((7pi)/4)=13(-sqrt2)/2`

Cartesian Form `=(6.5sqrt2, -6.5sqrt2)`

hope that helped