solve and irrational numbers



Hi,

It is fragment of code, where I try to solve system 
of 2 equations to find x1b and y1b


====================begin ================
/* outer circle with center at origin  */
r0:400; /* radius */
x0:0;   /* realpart of center */
y0:0;   /* imagpart of center */

/* I want to pack in 3 equall circles :
I can compute its radius : */

a1:(1 + 2 / sqrt(3)); /* http://www2.stetson.edu/~efriedma/cirincir/ */ /
* float is needed for solve */
r1:r0/a1;
x1a:0;
y1a:(r0-r1);

e2:(x0-x1b)^2+(y0-y1b)^2 -(r0-r1)^2=0; /* 0 and 1a */
e3:(x1a-x1b)^2+(y1a-y1b)^2 -(r1+r1)^2=0; /* 1a and 1b */
s1b:solve([e2,e3],[x1b,y1b]);
=============== end =========================


s1b is empty = no results.

When I change 
a1:(1 + 2 / sqrt(3));
to 
a1:float(1 + 2 / sqrt(3));

It gives good solutions.

Adam