What is the definite integral of zero?

1 Answer

If you mean #int_a^b0dx#, it is equal to zero.

This can be seen in a number of ways.

  • Intuitively, the area under the graph of the null function is always zero, no matter over what interval we chose to evaluate it. Therefore, #int_a^b 0 dx# should be equal to #0#, although this isn't an actual computation.

  • Note the derivative of a constant function #d/(dx)C=0#.
    By the Fundamental Theorem of Calculus, we get
    #int_a^b 0 dx = int_a^b d/(dx) C dx = C(b) - C(a) = C - C = 0#

  • Consider the Riemann Sums of the function #0#:
    #sum_i^n f(x_i) Delta x_i = sum_i^n 0 Delta x_i ,#
    where #Delta x_i# are the lengths of the divisions of the interval #[a,b]#.
    No matter how we choose to divide the interval, this sum is always equal to #0#, since #0 Delta x_i=0#.
    Therefore, the limit
    #lim_(n to oo) sum_i^n 0 Delta x_i = int_a^b 0 dx = 0#