TangentLine(l, point(A, 0, 1), circle(c, [point(C, 0, 1), 1]))

Under geometry package if I use the command Tangentline, and if I want to change either the point of the circle, then 

Error, (in geometry:-line) the first argument is expected of type name

How I make it overwrite l each time? So I don't have to rename the tangents each time? 

 

Dear friends, 

Lets say I have this procedure here. 
graph := proc(fn::anything, t::{integer, name}) if type(t, integer) then return fn; else return plot(fn, gridlines); end if; end proc

Currently it returns a function from input if I provide an addtional argument in integer form. And it provides the graph for the function if I include an extra argument of type name. 

However I would like to do (if possible) is to using the same proc to make the parameter t optional instead. Meaning if type 

graph(x^2)  then it only returns the input and if I type graph(x^2,g) then instead it returns the graph of the input function. 

Is this possible to do? I have this paragraph in the help files https://www.maplesoft.com/support/help/Maple/view.aspx?path=parameter_classes#optional But I am not sure if thats the way to go? 

Hope somebody has a hint/idea? Best regards 

If I have a line on the form a*x+by+c = 0 which command do I use to rearrange it to y = m*x+b ?

Other than isolate? 

Many thanks in advance.

Any with an idea on how to determine the Inflexition points on a discrete data set in Maple? I can only find stuff online on how to in Matlab, but not in Maple. 

Any suggestions on how to do it in Maple? 

Lets say I have a circle with the eqn 

x^2 + y^2 - 10*x - 75 = 0

Is there a command which would allow me to convert the above to (x-5)^2+y^2=100 ? 

I have tried to both collect, factor but neither of these work for obvious reason. 

So any idea/surgestion on which command one could use? 

Many thanks in advance.