A line tangent to the graph of the function y=f(x) at the point x = a forms an π/3 with y-axis and at x = b an angle π/4 with x-axis then
∫ab f′′(x)dx is
1−13
−π12
π12
3−1
f′(a)=tanπ2−π3=tanπ6=13 and f′(b)=
tanπ4=1, so
∫ab f′′(x)dx=f′(b)−f′(a)=1−13.