T[k_, f_] = 
      16*k^4/(16*k^4 + 8*k^2*f^2 + 8*k^2*f^2*Cos[2*k] + 2*f^4 - 
              2*f^4*Cos[2*k] + 8*k*f^3*Sin[2*k])

\(\(\(g1\)\(=\)\(Plot[T[k, 10], {k, 0, 10}, Frame -> True, 
        PlotRange -> All]\)\(
\)\)\)

Display["p4plot1.eps", g1, "EPS"]

denom[k_, f_] = 
      16*k^4  +  8*k^2*f^2 + 8*k^2*f^2*Cos[2*k] + 2*f^4 - 2*f^4*Cos[2*k] + 
        8*k*f^3*Sin[2*k]

cr[k_, 
        f_] = (16*k^4  +  4*k^2*f^2 + 4*k^2*f^2*Cos[2*k] + 
            2*k*f^3*Sin[2*k])/denom[k, f]

ci[k_, 
        f_] = (-8*k^3*f + 4*k^2*f^2*Sin[2*k] - 2*k*f^3 + 
            2*k*f^3*Cos[2*k])/denom[k, f]

dr[k_, 
        f_] = (8*k^3*f*Sin[2*k] - 8*k^2*f^2*Cos[2*k] - 2*k*f^3*Sin[2*k])/
        denom[k, f]

di[k_, 
        f_] = (-8*k^3*f*Cos[2*k] - 8*k^2*f^2*Sin[2*k] + 
            2*k*f^3*Cos[2*k] - 2*k*f^3)/denom[k, f]

ϕ[k_, f_, x_] = 
      cr[k, f]*Cos[k*x] - ci[k, f]*Sin[k*x] + dr[k, f]*Cos[k*x] + 
        di[k, f]*Sin[k*x]

g2 = 
      Plot[ϕ[2.6, 10, x], {x, -1, 1}, Frame -> True, 
        PlotRange -> All]

Display["p4plot2.eps", g2, "EPS"]

g3 = 
      Plot[ϕ[5.5, 10, x], {x, -1, 1}, Frame -> True, 
        PlotRange -> All]

Display["p4plot3.eps", g3, "EPS"]