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Trapezoid

Native Peruvian architecture makes heavy use of the trapezoid for stability in earthquakes. (The Spaniards thought they were primitive as they didn't use arches ... but most of the Spanish buildings have collapsed or had to be rebuilt).

It's especially apparent in their doorways and windows.

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Other examples with licensing such that I don't want to embed it:

Trapezoids are also found in cabinet joinery, specifically dovetail joints.

Segment of a Circle

Most architectural arches are based on segments of circles, particularly those in Roman architecture:

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Chinese architecture tends to favor segmental arches (which the Romans also used), rather than full rounded arches:

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See also arch bridges and barrel vaults. If you want sophomoric humor, also consider the groin vault (when made with round barrel vaults, not pointed barrel vaults).

Parabola

There are also Parabolic Arches:

Parallel lines cut by a transversal

Runways at large airports. They typically have taxiway parallel to the runway, and in windy areas have a second (or even third) pair to avoid takeoffs/landings into a cross wind. BWI is a good example, but I was having difficulty finding public domain images. Here's one of O'Hare:

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