Question

what is the of a parabola inscribed in rectangle 30cm long and 22cm wide?

Answer 1

x^2=4py

At x=22/2 = 11 , y = 30

So p = x^2/4y = 11^2/4(30)=121/120 (btw, this is the focus)

So you equation of a parabola is

y = x^2 / 4 * p = x^2 /(4*121/120) = 30x^2/121

http://www.wolframalpha.com/input/?i=plot+30*x%5E2%2F121%2C+-11%3C%3Dx%3C%3D11

Answer 2

may I know what formula did u use?

Answer 3

of course - http://en.wikipedia.org/wiki/Parabola

Since this is centered at the origin and symmetric about the y-axis, we use x^2=4py.

Does this make sense?