Write down the expression, involving to x=a definite integral,that gives the area between the graph of f and the x-axis,from x=7pi/5 to x=8pi/5.

Mathematics by Geoffrey

The question is about the function

f(x)=-(x+1)sin(5x)

a)explain why the graph of f lies on or above the x-axis for all values of x in the interval [7pi/5, 8pi/5]

b)Write down the expression, involving to x=a definite integral,that gives the area between the graph of f and the x-axis,from x=7pi/5 to x=8pi/5.

c) use integration by parts to find area described in part b), giving both the exact answer and an approximation to three decimal places.