- #1
yungman
- 5,718
- 241
An ellipse is represented by [itex] \rho(t)^2=x^2(t) + y^2(t)[/itex] where [itex]\rho(t)[/itex] is the distance from origin to the ellipse at a given time.
The way the article used to find the major and minor axis is the take the derivative [itex]\frac{d(\rho^2(t))}{d t}=0[/itex] to find the maximum and minimum.
My question is why it use [itex]\frac{d(\rho^2(t))}{d t}=0[/itex], not [itex]\frac{d\rho(t)}{d t}=0[/itex]?
The way the article used to find the major and minor axis is the take the derivative [itex]\frac{d(\rho^2(t))}{d t}=0[/itex] to find the maximum and minimum.
My question is why it use [itex]\frac{d(\rho^2(t))}{d t}=0[/itex], not [itex]\frac{d\rho(t)}{d t}=0[/itex]?