Chapter 11 - Section 11.1 - Parabolas - 11.1 Exercises - Page 788: 18

(a) Focus: $F(0,1)$ Directrix: $y=-1$ $Focal~diameter=4$ (b)

Equation of a parabola with vertical axis: $x^2=4py$ $y=\frac{1}{4}x^2$ $x^2=4y$ $4p=4$ $p=1$ Focus: $F(0,p)=F(0,1)$ Directrix: $y=-p=-1$ $Focal~diameter=|4p|=4$