Hi, i tried to derivate the equation of the ellipse and i managed to do so.

Then i tried the same with the Hyperbola. Though the equations are almost the same i didnt manage to derivate it.

Ellips:

((x-xo)^2/a^2)+((y-yo)^2/b^2)=1

Hyperbola:

((x-xo)^2/a^2)-((y-yo)^2/b^2)=1

Look at this material:

http://leto.vxu.se/msi/utb/exarb/2000/0072.pdf
Its on Swedish though but the math is the same

Page 7 for the ellips and page 13 for the Hyperbola.

On page 13 they derivate the Hyperbola but for me it seems that the equation isnt correct. I dont see how they exactly get from the third to fourth row.

Can anyone show me so i understand?