# Approximates the area under the function f over a
# given interval
# Make sure the file f.R is contained in the same folder
# as this file
source("f.R")
# Input: xmin = left end of interval
# xmax = right end of interval
# n = how many rectangles to use
# Output: sum = approx of the area under f over a
# given interval
Rrect = function(xmin, xmax, n) {
# Initially set sum to zero
sum = 0
# Calculate the width of the rectangles
deltax = (xmax - xmin) / n
# One pass through the for loop for each rectangle
for (i in 1:n) {
# Add onto the current sum the area of the current triangle
sum = sum + f(xmin + i*deltax) * deltax
}
return(sum)
}