kill(all)$

van=facebook.com/LearningCalculs$

y(x):=x;

'integrate('f(x),x,a,b);

areaUnderCurve(f,x, a, b):=integrate(f,x,a,b);

areaUnderCurve(x,x,a,b);

areaUnderCurve(f,x):=integrate(f,x) + constant;

areaUnderCurve(x,x);

integrate(f(x),g(x),a,b);