Integrate[(x - 3)^16, {x, 2, 3}]

Integrate[x/Sqrt[4  -  x^4], {x, -1, 1}]

Integrate[Abs[x^3  -  3  x^2  +  2  x],  {x, 0, 2}]

N[Pi/4]

p  =  
      Plot[1/(1 + x^2), {x, 0, 1},  AxesOrigin -> {0, 0}, 
        PlotRange -> {0, 1.05},  Ticks -> {{0,  .5, 1}, {0.5, 1}}]

\(\(r\  = \ 
      Graphics[{Line[{{0,  .8}, { .5,  .8}, { .5, 0}}], 
			
          Line[{{ .5,  .5}, {1,  .5}, {1, 0}}]}]; \)\)

Show[p, r]