On the help page, the description says the remove function does the opposite of select.
when I run:

remove(has, D[1](xx[0]), {xx[0]})

it gives: D[1]()

while: select(has, D[1](xx[0]), {xx[0]})

produces: D[1](xx[0])

I find this during programming. 

Is there a way to remove the whole expression "D[1](xx[0])"

Many thanks!

abs(-((-(1/20)*sqrt(5)-1/20)*cos((1/5)*Pi)-(1/20)*sqrt(2)*sqrt(5-sqrt(5))*sin((1/5)*Pi))*24^(1/5)*5^(3/5)-I*((1/20)*sqrt(2)*sqrt(5-sqrt(5))*cos((1/5)*Pi)+(-(1/20)*sqrt(5)-1/20)*sin((1/5)*Pi))*24^(1/5)*5^(3/5))

I am trying to compute the modulus the above complex number. However, the "abs" command does not affect the complex expression. Any reason for this?

Many thanks!

Is there any way to solve sin(x)=0 with solutions x=k*pi in Maple?

Many thanks!

I tried to find the root distritubion of a polynomial? 

When p=1, q=3, the following command works.

with(plots):

eq:=u^(2*q)+1-2*K*u^(q-p);

p:=1;   q:=3;

unitcircle:=implicitplot(x^2+y^2 = 1, x = -1 .. 1, y = -1 .. 1, scaling = constrained);

animate(complexplot,[[solve(eq, u)],style = point,symbolsize=10,color="red"],frames=50,K=-1..1,background=unitcircle, scaling=constrained, trace=20 );

However, when I tried p=2, q=3, only one root was shown on the animation.  

But   "complexplot([solve(eq,u)],style=point)"      showed  6 roots anyway.

I have no idea what was wrong. 

Dear all,

The results I get from calcultion are usually not in compact forms, so I want to do some simplifying work. And I come up with some questions.

If I write the following expression, the factor command works:
> beta[c]^3/exp(I*omega[c]*tau)-beta[c]^2/(exp(I*omega[c]*tau))^2-2*beta[c]^2+2*beta[c]/exp(I*omega[c]*tau)+beta[c]*exp(I*omega[c]*tau)-1;
> factor(%);
   
However,when I write the above expressoin as following,  factor doesn't work