## anonymous one year ago Convert (-5, pi/4) to rectangular coordinates. A. (sqrt(2) / 2, sqrt(2) / 2) B. (5 sqrt(3) / 2, 5/ 2) C. (5 sqrt(2) / 2, 5 sqrt(2) / 2) D. (-5 sqrt(2) / 2, -5 sqrt(2) / 2)

1. anonymous

I am thinking that it would be B. However I am having trouble understanding how to get my answer.

2. anonymous

$x = rcos \theta$$y= rsin \theta$

3. anonymous

$x = (-5)\cos(\frac{ \pi }{ 4 })$$y = (-5)\sin(\frac{ \pi }{ 4 })$

4. anonymous

I don't get any of the answers :(

5. anonymous

yes. last step is to use a unit circle to get sin (π/4) and cos (π/4)

6. anonymous

45?

7. anonymous

Oh sin and cos of 45?

8. anonymous

yes

9. anonymous

It would be A?

10. anonymous

D. A doesn't have -5 for r

11. anonymous

Oh you just said the answer didn't you

12. anonymous

yes r can be negative. |dw:1435189073642:dw|

13. anonymous

Oh I see now! D is the answer! Thank you for your time

14. anonymous

no problem. you're welcome