Question 1081076
given:
{{{e =5/2}}}, and directrix at {{{y=4}}}


The standard form for the polar conics is:

{{{r = ep/(1 + e*sin(theta))}}}


{{{r = (5/2)4 / (1 + (5/2)sin(theta))}}}


{{{r = (5/cross(2))cross(4)2 / (1 + (5/2)sin(theta))}}}


{{{r = (5*2) / (1 + (5/2)sin(theta))}}}


{{{r = 10 / (1 + (5/2)sin(theta))}}}

to make it clear what the parameters are, 
or, if you dislike fractions,


{{{r = 10 / (1/2)(2 + 5sin(theta))}}}


{{{r = 10*2/(2+5sin(theta))}}}


{{{r = 20/(2+5sin(theta))}}}