Question: simplify cosine expressions

Why does maple not simplify this expression any further:

-4*cos((1/5)*Pi)*m^3-4*cos((1/5)*Pi)*n^3-4*cos((1/5)*Pi)*p^3-4*cos((1/5)*Pi)*q^3+4*cos((2/5)*Pi)*m^3+4*cos((2/5)*Pi)*n^3+4*cos((2/5)*Pi)*p^3+4*cos((2/5)*Pi)*q^3-10*cos((1/5)*Pi)*p*q^2+10*cos((2/5)*Pi)*m^2*n+12*cos((2/5)*Pi)*m^2*p+12*cos((2/5)*Pi)*m^2*q+12*cos((2/5)*Pi)*m*n^2+10*cos((2/5)*Pi)*m*p^2+12*cos((2/5)*Pi)*m*q^2+12*cos((2/5)*Pi)*n^2*p+10*cos((2/5)*Pi)*n^2*q+12*cos((2/5)*Pi)*n*p^2+12*cos((2/5)*Pi)*n*q^2+12*cos((2/5)*Pi)*p^2*q+10*cos((2/5)*Pi)*p*q^2-10*cos((1/5)*Pi)*m^2*n-12*cos((1/5)*Pi)*m^2*p-12*cos((1/5)*Pi)*m^2*q-12*cos((1/5)*Pi)*m*n^2-10*cos((1/5)*Pi)*m*p^2-12*cos((1/5)*Pi)*m*q^2-12*cos((1/5)*Pi)*n^2*p-10*cos((1/5)*Pi)*n^2*q-12*cos((1/5)*Pi)*n*p^2-12*cos((1/5)*Pi)*n*q^2-12*cos((1/5)*Pi)*p^2*q-24*cos((1/5)*Pi)*m*n*p-24*cos((1/5)*Pi)*m*n*q-24*cos((1/5)*Pi)*m*p*q-24*cos((1/5)*Pi)*n*p*q+24*cos((2/5)*Pi)*m*n*p+24*cos((2/5)*Pi)*m*n*q+24*cos((2/5)*Pi)*m*p*q+24*cos((2/5)*Pi)*n*p*q+10*m*p^2+6*m*q^2+6*n^2*p+10*n^2*q+6*n*p^2+10*p*q^2+6*m*n^2+6*n*q^2+6*p^2*q+12*m*n*p+12*m*n*q+12*m*p*q+12*n*p*q+10*m^2*n+6*m^2*p+6*m^2*q+2*n^3+2*m^3+2*q^3+2*p^3