If one mentions the topic of evaluating definite integrals without the fundamental theorem of calculus, I think of things like ∫∞0sinxxdx or ∫∞−∞e−x2dx
i.e. "definite integral[s] proper" defined in this paper as "integral[s] whose value can be expressed in finite terms, although the indefinite integral of the subject of integration cannot be so determined."
However, at the freshman level, sometimes there is a point to evauating integrals without the fundamental theorem. For example, one can show by one of the simplest substitutions that ∫π/20sin2θdθ=∫π/20cos2θdθ,
and by a trivial trigonometric identity that their sum is ∫π/201dθ,
and some who post answers here go on to say that that is [11 θ ]π/20, but that is silly: one is just finding the area of a rectangle. Thus one evaluates both of (1) without antidifferentiating anything.
Q: What other examples exist of freshman-level integrals doable without antidifferentiating, and where some worthwhile pedagogical purpose can be served by proceeding without antidifferentiating?
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