How can I plot a vertical line say x = a in Maple 15 worksheet?

Thanks

Maple 15 does not allow me to do even small changes after executing even the smallest bit of command. Is there a way to overwrite this default setting and force Maple to undo? Do the newer versions of Maple provide this functionality and what is the purpose of undo getting deactivated after a command, at least it should be enabled for the input?

Greetings,

Maple 15 allows the following syntax

omega := sqrt(w0^2*(1+((z-zf)/z0)^2))

But it does not allow this one 

omega^2 := sqrt(w0^2*(1+((z-zf)/z0)^2))

Why is this so for functions and variables? Is there any way around this, I am really bugged by this issue. The Maple Math told me that the syntax was invalid so I had type the commands directly.

Is it possible in Maple 15 to solve an equation with a parameter for a given set of parameters? How can this be passed to the solve function, should I use some kind of list?  After obtaining the solution how can I assign the solutions to variables such as x1 for the first value of the parameter, x2 for the second value of the parameters and so on. Furthermore, is this possible with the fsolve command?

Thanks

Hello I am a Maple 15 user and I am using the command fsolve to solve for the intersection of two curves over a specified interval in x, namely from 0 to the lim defined in the Maple document. The specified interval contains asymptotes and when I specify the full interval only one of the three solutions is returned even if I can see that there are three distinct solutions by looking at the plot of RHS and LHS. Should I use another technique to find the solution or is my implementation of fsolve command wrong?

Thanks in advance

Download HW4Q2.mw