(ω/π)*(∫_0^((π/ω)))Sin[ω*
              t]*Cos[1*ω*t] \[DifferentialD]t

∫x*x \[DifferentialD]x

Sin[0]

Sin (0)

Cos[0]

Cos (0)

f[t] = Sin[t]

Plot f[x]

Plot[f, {t, 0, 10}]

pp = Plot[Evaluate[f], {t, 0, 10}]

f = Sin[t]

pp = Plot[Evaluate[f], {t, 0, 10}]

Plot[Evaluate[Sin[t], {t, 0, 10}]]

Plot[Evaluate[Sin[y], {y, 0, 10}]]

g = 
      0.5*Sin[y] - (2/(3*3.14159))*
          Cos[2*y] - (2/(15*3.14159))*Cos[4*y]

Plot[Evaluate[g], {y, 0, 10}]