a_{{p,q}}= \left( -4\, \left( \cos \left( {\frac {\pi }{q}} \right)
\right) ^{2}+8\, \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{2} \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{
2}-8\,\sin \left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {
\pi \,p}{q}} \right) \sin \left( {\frac {\pi }{q}} \right) \cos
\left( {\frac {\pi }{q}} \right) +3-4\, \left( \cos \left( {\frac {
\pi \,p}{q}} \right) \right) ^{2} \right) \left( \cos \left( {\frac
{\pi \, \left( q+1 \right) }{q}} \right) \right) ^{2}+ \left( -4\,
\left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2}+8\,
\left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2} \left(
\cos \left( {\frac {\pi }{q}} \right) \right) ^{2}-8\,\sin \left( {
\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}} \right)
\sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{q}}
\right) +3-4\, \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{2} \right) \left( \cos \left( {\frac {\pi \, \left( q+1
\right) p}{q}} \right) \right) ^{2}+ \left( 8\, \left( \cos \left( {
\frac {\pi }{q}} \right) \right) ^{2}-16\, \left( \cos \left( {\frac
{\pi \,p}{q}} \right) \right) ^{2} \left( \cos \left( {\frac {\pi }{q
}} \right) \right) ^{2}+16\,\sin \left( {\frac {\pi \,p}{q}} \right)
\cos \left( {\frac {\pi \,p}{q}} \right) \sin \left( {\frac {\pi }{q}}
\right) \cos \left( {\frac {\pi }{q}} \right) -6+8\, \left( \cos
\left( {\frac {\pi \,p}{q}} \right) \right) ^{2} \right) \left(
\cos \left( {\frac {\pi \, \left( q+1 \right) p}{q}} \right) \right)
^{2} \left( \cos \left( {\frac {\pi \, \left( q+1 \right) }{q}}
\right) \right) ^{2}+ \left( 8\,\sin \left( {\frac {\pi \,p}{q}}
\right) \cos \left( {\frac {\pi \,p}{q}} \right) \left( \cos \left(
{\frac {\pi }{q}} \right) \right) ^{4}-4\, \left( \cos \left( {\frac
{\pi }{q}} \right) \right) ^{3}\sin \left( {\frac {\pi }{q}} \right)
+8\, \left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2}
\left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{3}\sin
\left( {\frac {\pi }{q}} \right) -4\,\sin \left( {\frac {\pi \,p}{q}}
\right) \cos \left( {\frac {\pi \,p}{q}} \right) \left( \cos \left(
{\frac {\pi }{q}} \right) \right) ^{2}-8\,\sin \left( {\frac {\pi \,p
}{q}} \right) \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{3} \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{
2}-8\,\sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{
q}} \right) \left( \cos \left( {\frac {\pi \,p}{q}} \right) \right)
^{4}+\sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{q
}} \right) +4\, \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{2}\sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac
{\pi }{q}} \right) +4\,\sin \left( {\frac {\pi \,p}{q}} \right)
\left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{3}-\sin
\left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}}
\right) \right) \sin \left( {\frac {\pi \, \left( q+1 \right) }{q}}
\right) \cos \left( {\frac {\pi \, \left( q+1 \right) }{q}} \right)
\left( - \left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2
}+ \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2} \right)
^{-1}+ \left( 8\,\sin \left( {\frac {\pi \,p}{q}} \right) \cos \left(
{\frac {\pi \,p}{q}} \right) \left( \cos \left( {\frac {\pi }{q}}
\right) \right) ^{4}-4\, \left( \cos \left( {\frac {\pi }{q}}
\right) \right) ^{3}\sin \left( {\frac {\pi }{q}} \right) +8\,
\left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2} \left(
\cos \left( {\frac {\pi }{q}} \right) \right) ^{3}\sin \left( {\frac
{\pi }{q}} \right) -4\,\sin \left( {\frac {\pi \,p}{q}} \right) \cos
\left( {\frac {\pi \,p}{q}} \right) \left( \cos \left( {\frac {\pi }
{q}} \right) \right) ^{2}-8\,\sin \left( {\frac {\pi \,p}{q}}
\right) \left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{3
} \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2}-8\,\sin
\left( {\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{q}}
\right) \left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{4
}+\sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{q}}
\right) +4\, \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{2}\sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac
{\pi }{q}} \right) +4\,\sin \left( {\frac {\pi \,p}{q}} \right)
\left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{3}-\sin
\left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}}
\right) \right) \sin \left( {\frac {\pi \, \left( q+1 \right) p}{q}}
\right) \cos \left( {\frac {\pi \, \left( q+1 \right) p}{q}} \right)
\left( - \left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2
}+ \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2} \right)
^{-1}-2\, \left( 8\,\sin \left( {\frac {\pi \,p}{q}} \right) \cos
\left( {\frac {\pi \,p}{q}} \right) \left( \cos \left( {\frac {\pi }
{q}} \right) \right) ^{4}-4\, \left( \cos \left( {\frac {\pi }{q}}
\right) \right) ^{3}\sin \left( {\frac {\pi }{q}} \right) +8\,
\left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2} \left(
\cos \left( {\frac {\pi }{q}} \right) \right) ^{3}\sin \left( {\frac
{\pi }{q}} \right) -4\,\sin \left( {\frac {\pi \,p}{q}} \right) \cos
\left( {\frac {\pi \,p}{q}} \right) \left( \cos \left( {\frac {\pi }
{q}} \right) \right) ^{2}-8\,\sin \left( {\frac {\pi \,p}{q}}
\right) \left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{3
} \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2}-8\,\sin
\left( {\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{q}}
\right) \left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{4
}+\sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{q}}
\right) +4\, \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{2}\sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac
{\pi }{q}} \right) +4\,\sin \left( {\frac {\pi \,p}{q}} \right)
\left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{3}-\sin
\left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}}
\right) \right) \left( \cos \left( {\frac {\pi \, \left( q+1
\right) p}{q}} \right) \right) ^{2}\sin \left( {\frac {\pi \,
\left( q+1 \right) }{q}} \right) \cos \left( {\frac {\pi \, \left( q+
1 \right) }{q}} \right) \left( - \left( \cos \left( {\frac {\pi \,p}{
q}} \right) \right) ^{2}+ \left( \cos \left( {\frac {\pi }{q}}
\right) \right) ^{2} \right) ^{-1}-2\, \left( 8\,\sin \left( {\frac
{\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}} \right)
\left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{4}-4\,
\left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{3}\sin
\left( {\frac {\pi }{q}} \right) +8\, \left( \cos \left( {\frac {\pi
\,p}{q}} \right) \right) ^{2} \left( \cos \left( {\frac {\pi }{q}}
\right) \right) ^{3}\sin \left( {\frac {\pi }{q}} \right) -4\,\sin
\left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}}
\right) \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2}-8
\,\sin \left( {\frac {\pi \,p}{q}} \right) \left( \cos \left( {\frac
{\pi \,p}{q}} \right) \right) ^{3} \left( \cos \left( {\frac {\pi }{q
}} \right) \right) ^{2}-8\,\sin \left( {\frac {\pi }{q}} \right) \cos
\left( {\frac {\pi }{q}} \right) \left( \cos \left( {\frac {\pi \,p}
{q}} \right) \right) ^{4}+\sin \left( {\frac {\pi }{q}} \right) \cos
\left( {\frac {\pi }{q}} \right) +4\, \left( \cos \left( {\frac {\pi
\,p}{q}} \right) \right) ^{2}\sin \left( {\frac {\pi }{q}} \right)
\cos \left( {\frac {\pi }{q}} \right) +4\,\sin \left( {\frac {\pi \,p}
{q}} \right) \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{3}-\sin \left( {\frac {\pi \,p}{q}} \right) \cos \left( {
\frac {\pi \,p}{q}} \right) \right) \sin \left( {\frac {\pi \,
\left( q+1 \right) p}{q}} \right) \cos \left( {\frac {\pi \, \left( q
+1 \right) p}{q}} \right) \left( \cos \left( {\frac {\pi \, \left( q+
1 \right) }{q}} \right) \right) ^{2} \left( - \left( \cos \left( {
\frac {\pi \,p}{q}} \right) \right) ^{2}+ \left( \cos \left( {\frac {
\pi }{q}} \right) \right) ^{2} \right) ^{-1}+ \left( -8\, \left( \cos
\left( {\frac {\pi }{q}} \right) \right) ^{2}+16\, \left( \cos
\left( {\frac {\pi \,p}{q}} \right) \right) ^{2} \left( \cos \left(
{\frac {\pi }{q}} \right) \right) ^{2}-16\,\sin \left( {\frac {\pi \,
p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}} \right) \sin \left( {
\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{q}} \right) +6-8\,
\left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2}
\right) \sin \left( {\frac {\pi \, \left( q+1 \right) p}{q}} \right)
\cos \left( {\frac {\pi \, \left( q+1 \right) p}{q}} \right) \sin
\left( {\frac {\pi \, \left( q+1 \right) }{q}} \right) \cos \left( {
\frac {\pi \, \left( q+1 \right) }{q}} \right) - \left( -4\, \left(
\cos \left( {\frac {\pi }{q}} \right) \right) ^{2}+8\, \left( \cos
\left( {\frac {\pi \,p}{q}} \right) \right) ^{2} \left( \cos \left(
{\frac {\pi }{q}} \right) \right) ^{2}-8\,\sin \left( {\frac {\pi \,p
}{q}} \right) \cos \left( {\frac {\pi \,p}{q}} \right) \sin \left( {
\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{q}} \right) +3-4\,
\left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2}
\right) \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2}-
\left( -4\, \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2
}+8\, \left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2}
\left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2}-8\,\sin
\left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}}
\right) \sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac {
\pi }{q}} \right) +3-4\, \left( \cos \left( {\frac {\pi \,p}{q}}
\right) \right) ^{2} \right) \left( \cos \left( {\frac {\pi \,p}{q}
} \right) \right) ^{2}- \left( 8\, \left( \cos \left( {\frac {\pi }{q
}} \right) \right) ^{2}-16\, \left( \cos \left( {\frac {\pi \,p}{q}}
\right) \right) ^{2} \left( \cos \left( {\frac {\pi }{q}} \right)
\right) ^{2}+16\,\sin \left( {\frac {\pi \,p}{q}} \right) \cos
\left( {\frac {\pi \,p}{q}} \right) \sin \left( {\frac {\pi }{q}}
\right) \cos \left( {\frac {\pi }{q}} \right) -6+8\, \left( \cos
\left( {\frac {\pi \,p}{q}} \right) \right) ^{2} \right) \left(
\cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2} \left( \cos
\left( {\frac {\pi }{q}} \right) \right) ^{2}- \left( 8\,\sin
\left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}}
\right) \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{4}-4
\, \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{3}\sin
\left( {\frac {\pi }{q}} \right) +8\, \left( \cos \left( {\frac {\pi
\,p}{q}} \right) \right) ^{2} \left( \cos \left( {\frac {\pi }{q}}
\right) \right) ^{3}\sin \left( {\frac {\pi }{q}} \right) -4\,\sin
\left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}}
\right) \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2}-8
\,\sin \left( {\frac {\pi \,p}{q}} \right) \left( \cos \left( {\frac
{\pi \,p}{q}} \right) \right) ^{3} \left( \cos \left( {\frac {\pi }{q
}} \right) \right) ^{2}-8\,\sin \left( {\frac {\pi }{q}} \right) \cos
\left( {\frac {\pi }{q}} \right) \left( \cos \left( {\frac {\pi \,p}
{q}} \right) \right) ^{4}+\sin \left( {\frac {\pi }{q}} \right) \cos
\left( {\frac {\pi }{q}} \right) +4\, \left( \cos \left( {\frac {\pi
\,p}{q}} \right) \right) ^{2}\sin \left( {\frac {\pi }{q}} \right)
\cos \left( {\frac {\pi }{q}} \right) +4\,\sin \left( {\frac {\pi \,p}
{q}} \right) \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{3}-\sin \left( {\frac {\pi \,p}{q}} \right) \cos \left( {
\frac {\pi \,p}{q}} \right) \right) \sin \left( {\frac {\pi }{q}}
\right) \cos \left( {\frac {\pi }{q}} \right) \left( - \left( \cos
\left( {\frac {\pi \,p}{q}} \right) \right) ^{2}+ \left( \cos
\left( {\frac {\pi }{q}} \right) \right) ^{2} \right) ^{-1}- \left(
8\,\sin \left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,
p}{q}} \right) \left( \cos \left( {\frac {\pi }{q}} \right) \right)
^{4}-4\, \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{3}
\sin \left( {\frac {\pi }{q}} \right) +8\, \left( \cos \left( {\frac {
\pi \,p}{q}} \right) \right) ^{2} \left( \cos \left( {\frac {\pi }{q}
} \right) \right) ^{3}\sin \left( {\frac {\pi }{q}} \right) -4\,\sin
\left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}}
\right) \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2}-8
\,\sin \left( {\frac {\pi \,p}{q}} \right) \left( \cos \left( {\frac
{\pi \,p}{q}} \right) \right) ^{3} \left( \cos \left( {\frac {\pi }{q
}} \right) \right) ^{2}-8\,\sin \left( {\frac {\pi }{q}} \right) \cos
\left( {\frac {\pi }{q}} \right) \left( \cos \left( {\frac {\pi \,p}
{q}} \right) \right) ^{4}+\sin \left( {\frac {\pi }{q}} \right) \cos
\left( {\frac {\pi }{q}} \right) +4\, \left( \cos \left( {\frac {\pi
\,p}{q}} \right) \right) ^{2}\sin \left( {\frac {\pi }{q}} \right)
\cos \left( {\frac {\pi }{q}} \right) +4\,\sin \left( {\frac {\pi \,p}
{q}} \right) \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{3}-\sin \left( {\frac {\pi \,p}{q}} \right) \cos \left( {
\frac {\pi \,p}{q}} \right) \right) \sin \left( {\frac {\pi \,p}{q}}
\right) \cos \left( {\frac {\pi \,p}{q}} \right) \left( - \left(
\cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2}+ \left( \cos
\left( {\frac {\pi }{q}} \right) \right) ^{2} \right) ^{-1}+2\,
\left( 8\,\sin \left( {\frac {\pi \,p}{q}} \right) \cos \left( {
\frac {\pi \,p}{q}} \right) \left( \cos \left( {\frac {\pi }{q}}
\right) \right) ^{4}-4\, \left( \cos \left( {\frac {\pi }{q}}
\right) \right) ^{3}\sin \left( {\frac {\pi }{q}} \right) +8\,
\left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2} \left(
\cos \left( {\frac {\pi }{q}} \right) \right) ^{3}\sin \left( {\frac
{\pi }{q}} \right) -4\,\sin \left( {\frac {\pi \,p}{q}} \right) \cos
\left( {\frac {\pi \,p}{q}} \right) \left( \cos \left( {\frac {\pi }
{q}} \right) \right) ^{2}-8\,\sin \left( {\frac {\pi \,p}{q}}
\right) \left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{3
} \left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2}-8\,\sin
\left( {\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{q}}
\right) \left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{4
}+\sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{q}}
\right) +4\, \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{2}\sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac
{\pi }{q}} \right) +4\,\sin \left( {\frac {\pi \,p}{q}} \right)
\left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{3}-\sin
\left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}}
\right) \right) \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{2}\sin \left( {\frac {\pi }{q}} \right) \cos \left( {\frac
{\pi }{q}} \right) \left( - \left( \cos \left( {\frac {\pi \,p}{q}}
\right) \right) ^{2}+ \left( \cos \left( {\frac {\pi }{q}} \right)
\right) ^{2} \right) ^{-1}+2\, \left( 8\,\sin \left( {\frac {\pi \,p}
{q}} \right) \cos \left( {\frac {\pi \,p}{q}} \right) \left( \cos
\left( {\frac {\pi }{q}} \right) \right) ^{4}-4\, \left( \cos
\left( {\frac {\pi }{q}} \right) \right) ^{3}\sin \left( {\frac {
\pi }{q}} \right) +8\, \left( \cos \left( {\frac {\pi \,p}{q}}
\right) \right) ^{2} \left( \cos \left( {\frac {\pi }{q}} \right)
\right) ^{3}\sin \left( {\frac {\pi }{q}} \right) -4\,\sin \left( {
\frac {\pi \,p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}} \right)
\left( \cos \left( {\frac {\pi }{q}} \right) \right) ^{2}-8\,\sin
\left( {\frac {\pi \,p}{q}} \right) \left( \cos \left( {\frac {\pi
\,p}{q}} \right) \right) ^{3} \left( \cos \left( {\frac {\pi }{q}}
\right) \right) ^{2}-8\,\sin \left( {\frac {\pi }{q}} \right) \cos
\left( {\frac {\pi }{q}} \right) \left( \cos \left( {\frac {\pi \,p}
{q}} \right) \right) ^{4}+\sin \left( {\frac {\pi }{q}} \right) \cos
\left( {\frac {\pi }{q}} \right) +4\, \left( \cos \left( {\frac {\pi
\,p}{q}} \right) \right) ^{2}\sin \left( {\frac {\pi }{q}} \right)
\cos \left( {\frac {\pi }{q}} \right) +4\,\sin \left( {\frac {\pi \,p}
{q}} \right) \left( \cos \left( {\frac {\pi \,p}{q}} \right)
\right) ^{3}-\sin \left( {\frac {\pi \,p}{q}} \right) \cos \left( {
\frac {\pi \,p}{q}} \right) \right) \sin \left( {\frac {\pi \,p}{q}}
\right) \cos \left( {\frac {\pi \,p}{q}} \right) \left( \cos \left(
{\frac {\pi }{q}} \right) \right) ^{2} \left( - \left( \cos \left( {
\frac {\pi \,p}{q}} \right) \right) ^{2}+ \left( \cos \left( {\frac {
\pi }{q}} \right) \right) ^{2} \right) ^{-1}- \left( -8\, \left( \cos
\left( {\frac {\pi }{q}} \right) \right) ^{2}+16\, \left( \cos
\left( {\frac {\pi \,p}{q}} \right) \right) ^{2} \left( \cos \left(
{\frac {\pi }{q}} \right) \right) ^{2}-16\,\sin \left( {\frac {\pi \,
p}{q}} \right) \cos \left( {\frac {\pi \,p}{q}} \right) \sin \left( {
\frac {\pi }{q}} \right) \cos \left( {\frac {\pi }{q}} \right) +6-8\,
\left( \cos \left( {\frac {\pi \,p}{q}} \right) \right) ^{2}
\right) \sin \left( {\frac {\pi \,p}{q}} \right) \cos \left( {\frac {
\pi \,p}{q}} \right) \sin \left( {\frac {\pi }{q}} \right) \cos
\left( {\frac {\pi }{q}} \right)
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