unnecessary prompt while using defined functions

Hello,

    I am defining some functions that involve subscripted variables, trig functions, and sqrt.   There are no conditional 
expressions involved.  When I use these functions I get a prompt asking for  positive, negative, or zero.  

inc(1)    // no prompt 
sca(1)  // I get following prompts

Is  %mu[1]   positive, negative, or zero? pos;
Is  %rho[1]   positive, negative, or zero? pos;
Is  2 * %mu[1] + %lambda[1]   positive, negative, or zero? pos;

I do not understand why I am getting a prompt which happens in sca function and not in inc function.    I should not be getting any prompt.  Here is the code  (WxMaxima 0.7.1)
 
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load(linearalgebra);
load(eigen);
load("diag");
load("mactex-utilities.lisp");
load("lrats");

vel(ir):=[sqrt(%mu[ir])/sqrt(%rho[ir]),
           sqrt(2*%mu[ir]+%lambda[ir])/sqrt(%rho[ir]),sqrt(%mu[ir])/sqrt(%rho[ir])]$

_Av:lambda([ir,th],[sqrt(%mu[ir])/sqrt(%rho[ir]),matrix([-2*sqrt(%mu[ir])*sqrt(%rho[ir])*cos(th)*sin(th)],
[2*sqrt(%mu[ir])*sqrt(%rho[ir])*cos(th)*sin(th)],[0],[0],[0],
[sqrt(%mu[ir])*sqrt(%rho[ir])-2*sqrt(%mu[ir])*sqrt(%rho[ir])*sin(th)^2],[-sin(th)],[cos(th)],[0])])$

_Al:lambda([ir,th],[sqrt(2*%mu[ir]+%lambda[ir])/sqrt(%rho[ir]),
  matrix([(2*%mu[ir]*sqrt(%rho[ir])*sin(th)^2+(-2*%mu[ir]-%lambda[ir])*sqrt(%rho[ir]))/sqrt(2*%mu[ir]+%lambda[ir])],
	[-(2*%mu[ir]*sqrt(%rho[ir])*sin(th)^2+%lambda[ir]*sqrt(%rho[ir]))/sqrt(2*%mu[ir]+%lambda[ir])],
	[-(%lambda[ir]*sqrt(%rho[ir]))/sqrt(2*%mu[ir]+%lambda[ir])],[0],[0],
	[-(2*%mu[ir]*sqrt(%rho[ir])*cos(th)*sin(th))/sqrt(2*%mu[ir]+%lambda[ir])],[cos(th)],[sin(th)],[0])])$

_Ah:lambda([ir,th],[sqrt(%mu[ir])/sqrt(%rho[ir]),matrix([0],[0],[0],[-sqrt(%mu[ir])*sqrt(%rho[ir])*sin(th)],
             [-sqrt(%mu[ir])*sqrt(%rho[ir])*cos(th)],[0],[0],[0],[1])])$


inc(n):=block([p,th],for m:1 thru 3 do
           th[m]:%theta[n,m], addcol(_Ah(n,th[1])[2] * exp(%i * y* sin(th[1])/vel(n)[3]),
		      _Av(n,th[2])[2]* exp(%i * y* sin(th[2])/vel(n)[2]),
			  _Al(n,th[3])[2]* exp(%i * y* sin(th[3])/vel(n)[1])));

sca(n):=block([p,th],for m:4 thru 6 do
           th[m]:%theta[n,m], addcol(_Ah(n,th[4])[2]*exp(-%i * y* sin(th[4])/vel(n)[3]),
		   _Av(n,th[5])[2]*exp(-%i * y* sin(th[5])/vel(n)[2]),_Al(n,th[6])[2]*exp(-%i * y* sin(th[6])/vel(n)[1])));
		   
tot(n):=addcol(inc(n),sca(n));	

 
inc(1);
sca(1);

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Thank you for your help.

Ram Kochhar