# Parabola's focus

• May 9th 2007, 04:40 PM
ijleyton
Parabola's focus
How can i find the focus of the parabola/arc if i know the equation
(y= {1/125}x^2) and the distance between the endpoints (100m).
I've looked for an explanation but i havent been able to find a good one, if someone can point to an easy to understand website that'd be great. THx
• May 9th 2007, 04:56 PM
topsquark
Quote:

Originally Posted by ijleyton
How can i find the focus of the parabola/arc if i know the equation
(y= {1/125}x^2) and the distance between the endpoints (100m).
I've looked for an explanation but i havent been able to find a good one, if someone can point to an easy to understand website that'd be great. THx

Ummmm...yeah! What Soroban is about to say. :)

-Dan
• May 9th 2007, 05:07 PM
Soroban
Hello, ijleyton!

Quote:

How can i find the focus of the parabola if i know the equation: .y .= .(1/125)x²

We already know that the parabola opens upward and its vertex is the origin.

The general form (for this parabola) is: . .= .4py
. . where p is the distance from the vertex to the focus.

Your parabola is: . .= .125y

Hence: .4p = 125 . . . .p = 125/4

Therefore, the focus is at: .(0, 31¼)