Computer Science I / The Definite Integral and Area
Practice question · Sort into groups

A curve is integrated from left to right. Sort each portion by how it contributes to the definite integral.

Groups: Adds a positive amount · Subtracts · Contributes nothing

Hints
  1. The height f(x) enters each rectangle's area with its own sign.
  2. A rectangle of zero height has zero area no matter how wide it is.
Show the answer

Adds a positive amount: A stretch where the curve sits above the axis

Subtracts: A stretch where the curve dips below the axis, A deep trough well below the axis

Contributes nothing: A stretch where the curve lies exactly on the axis

Why

The sign of f decides the sign of every rectangle in the sum, so dips below the axis subtract. This is why an odd function integrated over a symmetric interval returns zero even though it plainly encloses area.

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