This is on the 2008 Free response AP Calc AB exam- #4a.

Let f be the function given by f(x)=(lnx)(sinx). The figure above shows the graph of f for 0<=x<=2pi. The function g is defined by int{1,x} f(t)dt for 0<x<=2pi.

a) find g(1). I don't get why it is equal to zero. Like is there a way to tell from the graph or do it analytically?

1 answer

well, g(1) = int{1,1} f(t)dt

if the integral is done over an interval of zero width, its value is zero.