## sarah1017 Group Title What is the standard form of the equation of an ellipse with foci at (+-3,0) and co-vertices at (0,+-5)? Please show all steps! 4 months ago 4 months ago

1. ganeshie8 Group Title

|dw:1393563390845:dw|

2. ganeshie8 Group Title

|dw:1393563452971:dw|

3. ganeshie8 Group Title

|dw:1393563500603:dw|

4. ganeshie8 Group Title

b = 5 a = ?

5. ganeshie8 Group Title

if u can find a, u can write the equation of ellipse :- $$\large \frac{x^2}{a^2} + \frac{y^2}{b^2} = 1$$

6. ganeshie8 Group Title

any idea how to find "a" ? :)

7. sarah1017 Group Title

How do I find a? Is there a formula I have to follow?

8. ganeshie8 Group Title

u just need to knw how to find an unknown side in a right triangle

9. sleung Group Title

Use the pythagorean theorem.

10. ganeshie8 Group Title

|dw:1393563687257:dw|

11. ganeshie8 Group Title

a^2 = b^2 + c^2 a^2 = 5^2 + 3^2

12. ganeshie8 Group Title

simplify

13. sarah1017 Group Title

a^2=34

14. ganeshie8 Group Title

yes, you want "a" right ?

15. sarah1017 Group Title

Yes. So do I divide 34 by 2?

16. ganeshie8 Group Title

noo, you need to take "square ROOT" both sides

17. sleung Group Title

So $a=\sqrt{34}$

18. sarah1017 Group Title

5.83

19. ganeshie8 Group Title

actually im wrong, a^2 is enough as u put it earlier,,,, i see we dont need to find a -.-

20. ganeshie8 Group Title

directly plugin a^2 value in the equation

21. ganeshie8 Group Title

$$\large \frac{x^2}{34} + \frac{y^2}{25} = 1$$

22. ganeshie8 Group Title

^^final equation of ellipse

23. sarah1017 Group Title

Whoaaa that confused me. So that's the final equation, is the work we did before still correct? Well except the finding a parts?

24. ganeshie8 Group Title

everything is correct, you could even find "a", and plugin the "a" value back into the equaiton

25. ganeshie8 Group Title

but thats just extra unnecessary work

26. ganeshie8 Group Title

when u knw that u will be needing oly "a^2", why to find "a" ?

27. ganeshie8 Group Title

it wont be a mistake to find "a", its just pain to take square root of 34 lol.. .hope u get me :)

28. sarah1017 Group Title

I wasn't too sure how to do this at first so I just went with ya lol. I get it though. Thanks for your help :)

29. ganeshie8 Group Title

np :) u wlc :))

30. sarah1017 Group Title

:-)