Manipulate[
Graphics[Arrow[{{x1,f/.x->x1},{x2,g/.x->x2}}],Axes->True,ImageSize->300],
Grid[{
   {Control[{{f,Sin[x]},InputField}],Control[{{x1,Pi/2}}],InputField},
   {Control[{{g,Cos[x]},InputField}],Control[{{x2,Pi}}],InputField}}
   ]
]