Plot[Sin[x]/(1-Cos[x]),{x,0,Pi}]

Plot[Sin[x]^2/(1-Cos[x]),{x,0,Pi}]

NIntegrate[Sin[x]/(1-Cos[x]),{x,0,Pi}]

NIntegrate[Sin[x]^2/(1-Cos[x]),{x,0,Pi}]