@Carl Love this problem is in section 22.5.2 (The Particle Trajectory) in this book

it had no CD....

thanks alot for your help and support....

@Carl Love this problem is in newtons and kepler's laws book and this command is in this book.

i dont have dsnumsort.m and need tu read this for solve this problem ... i search for this file but can not find that...

please help ...

forgive me for my poor english

@Carl Love thanks

now i have another error in reading dsnumsort.m

"Error, could not open `dsnumsort.m` for reading"

how can find this file or open for reading?