Finding the Radius of a Paraboloid Spotlight

[r-soy]

Hi

In this queation which equation we use X^2 = 4ay or y^2 = 4ax and why ?

A paraboloid is formed by revolving a parabola about its axis . A spotlight in the form of a parabolid 5 inches deep has it's foucs 2 inches from the vertex . Find to one decimal place , the raduis R of the opening of the spotlight ...

 

[Mr.Miyagi]

Both equations represent the same relation. The names of variables have just been flipped. In the first equation the spotlight would be pointing along the y-axis. In the second equation it would be pointing along the x-axis.