According to help here  on display, it says "The options parameter can include plot options as described in the plot/option "  and when  I go to the plots/option I see legend there. But when I try to use it, I get an error that plots:-display does not accept the legened option.

I am generating 2 plots, and use display() to show them on one axes. But need to add a legend as well. Is there a correct way to do this? 

restart:
with(DynamicSystems):
with(plots):
sys := TransferFunction(1/(s^2+0.2*s+1)): 
p1:=ResponsePlot(sys, Step(),duration=50,color=red):
p2:=ImpulseResponsePlot(sys,50);
display([p1,p2],axes=boxed, title=`step and impulse reponses`,legend=["step","impulse"]);

Now if I add legend, it fail

display([p1,p2],axes=boxed, title=`step and impulse reponses`,legend=["step","impulse"]);

I am sure I am doing something wrong. How to add legend to display? I can't use plot([...]) since the plots are allready generated by other Maple functions.

One can write 

restart;
alias(C=binomial);
C(4,2);

or

restart;
C:=binomial;
C(4,2);

and then both work the same. In the first case, the replacement of "C" by "binomial" is done at parsing time before evluator gets hold of the code, while in the second case, the replacement is done at run-time (evaluation).

So alias will be more efficient and more safe, I assume.

Is that all there is to it, or are there other more subtle and important reasons to use alias vs. :=  when one want to bind long name to smaller ones to save on typing.

I am newbie in Maple, and trying to understand when to use operator `if` as I see in some code vs. normal if. This is in context if using map()

I noticed I can write

A:=[seq(i,i=1..10)];
f:=x->x^2;
map(x->`if`(x<5,f(x),NULL),A);

or

map(x->if x<5 then f(x) fi,A);

And they both work the same. When should one use `if` vs. if? with the case of `if` I had to give a third argument NULL for the else part, while with using direct "if", I did not have to give the "else" part.

Also, suppose I want to use  IF .. THEN .. ELIF ... FI, then how would this be done using the operator syntax? in normal "if", I can write

A:=[seq(i,i=1..10)];
f:=x->x^2;
map(x->if x<5 then f(x) elif x=5 then x else x-1 fi,A);

Actually if I understand better when `if` is meant to be used vs. where the normal "if", I might understand more its use. 

ps. I did look at the help here but did not see it recommend when to use over the other (unless I overlooked it)

Is this a  false positive, where Maple is solving an ODE which is supposed to be unsolvable?

Accoding to http://www.maplesoft.com/compare/mathematica_analysis/Comparison_Maple_Mathmatica_DEs_Kamke.pdf and considering ODE 13

Maple 18.01 does give an answer for the above ODE. I verfied the ODE from the book as well. The answer returned by Maple is very large, but it does solve it in 195 CPU seconds. Therefore the question is: Is this a false result? Or is the above document have an error in it and ODE 13 is actually solvable?

restart;
ode:=diff(y(x), x$2)-(a*y(x)^2+b*x*y(x)+c*x^2+alpha*y(x)+beta*x+gamma)^(-3/2);
sol:=dsolve(ode,y(x)) assuming a::NonZero; #I get an answer with or without this assumption. The book has the assumption
odetest(sol,ode);

btw,

 odetest(sol,ode)

gives an error as well. May be this is related to the issue or not. Not sure now.

For some reason, Maple does not use \frac{}{} for things like 1/2 that can occur in an expression

restart;
expr:=1/2;
latex(expr);

            1/2

This make the generated code not good looking. For example using this in Maple:

latex(diff(y(x), x)+y(x)*cos(x)-(1/2)*sin(2*x) = 0);

produces this latex when proccessed:

When the latex is put inside a display in the document.  This is terrible. Is there a way to tell Latex to use \frac{}{} for fractions?