## anonymous one year ago Please help with a pre calc question. I will fan and medal best response.

1. anonymous

2. anonymous

@satellite73

3. anonymous

@ganeshie8

4. anonymous

The equation of an ellipse centered at the origin is $\frac{ x^2 }{ a^2}+\frac{ y^2 }{ b^2 }=1$ We know three points (0, 58), (21, 29), and (-21,29). If you substitute the points you should be able to solve for a and b.

5. anonymous

So: ((21^2)/a^2) +((29^2)/b^2) = 1?

6. anonymous

not really following you here... sorry

7. anonymous

yes that's right. And if you use (0,58) you can eliminate the x² part, which allows you to solve for b

8. anonymous

I'm sorry but can you just show me the steps with the information. Once I've done it once, it will make sense but right now I just don't get it.

9. anonymous

@Loser66 can you help?

10. anonymous

$\frac{ 0^2 }{ a^2 }+\frac{ 58^2 }{ b^2 }=1$ $\frac{ 58^2 }{ b^2 }=1$ Now you can solve for b

11. anonymous

wouldn't that mean that b=58?

12. anonymous

yes.

13. anonymous

oh ok. lol so how about finding a

14. anonymous

now put 58 into the equation you made above. $\frac{ 21^2 }{ a^2 }+\frac{ 29^2 }{ 58^2 }=1$

15. anonymous

now I just plug in a different pair of coordinates with b = 58?

16. anonymous

ok got it that all i need thanks

17. anonymous

you're welcome

18. anonymous

@peachpi sorry dude I thought I could get through the rest of the problem by myself but I got stuck can you help me finish it?

19. anonymous

@Loser66 can you help me finish the problem?

20. anonymous

I got this far: First find b from: (0^2/a^2) + (58^2/b^2) = 1 58^2/b^2 = 1 b = 58 Now find a: (21^2/a^2) + (29^2/58^2) = 1 (21^2/a^2) + 1/4 = 1 (21^2/a^2) = 3/4 or 0.75

21. Loser66

22. anonymous

he went offline

23. anonymous

|dw:1437955365294:dw|