kill(all)$

load(ntrig)$
load(atrig1)$

van=facebook.com/LearningCalculus$

rad(u):=%pi/180*u;

f(x):= tan(x) + tan(6*x) + tan(11*x);

X:expand(trigsimp(f(rad(6))));

trigrat(trigsimp(f(rad(6))));

atan(trigrat(trigsimp(f(rad(6)))));

float(%);

      Which is exactly 1,000,000 times the permeability of free space!
      Ref: http://www.physics.csbsju.edu/cgi-bin/twk/examples/F.html