Circumference = 2pi*r
r = radius
In our problem,
circumference = 36pi
r = ?
Let's plug our values into the formula above.
36pi = 2pi * r
Divide both sides by 2pi
18 = r
Im not sure what its asking.. whats the question?
So, notice, the focus point is at -7, 5, and the directrix is at y = -11.
keep in mind that the vertex is half-way between those two fellows, and the distance from the vertex to either one of them is "p" units, check the picture below.
with that focus point and that directrix, the half-way over the axis of symmetry will be -7, -3, that's where the vertex is at, and notice the distance "p", is 8 units.
since the parabola is opening upwards, "p" is positive 8.