en.wikipedia.org/wiki/Heron%27s_formula

In geometry, Heron's formula (sometimes called Hero's formula), named after Hero of Alexandria, gives the area of a triangle by requiring no arbitrary choice of side as base or vertex as origin, contrary to other formulas for the area of a triangle, .... The formula is credited to Heron (or Hero) of Alexandria, and a proof can be ...

www.basic-mathematics.com/proof-of-the-area-of-a-trapezoid.html

Find here a nifty proof of the area of a trapezoid using some basic math concepts.

www.mathopenref.com/trapezoidareaderive.html

This page describes how to derive the forumula for the area of a trapezoid, by creating a parallelogram from two congruent trapezoids. The equation is then ...

illuminations.nctm.org/Lesson.aspx?id=1893

The main portion of this lesson involves the derivation of an area formula for trapezoids. Prior to that, allow students some exploration time. Ask them to suggest ...

mathforum.org/library/drmath/view/55006.html

Date: 04/11/98 at 09:29:50 From: Dwight Subject: Trapezoid area formula proof We were told that the area of a trapezoid is half the sum of the parallel sides x the ...

www.khanacademy.org/math/basic-geo/basic-geo-area-and-perimeter/area-trap-composite/v/area-of-a-trapezoid-1

Area of a trapezoid is found with the formula, A=(a+b)/2 x h. Learn how to use the formula to find area of trapezoids.

math.stackexchange.com/questions/277025/trapezoid-area-proof-by-dividing-it-into-two-triangles

I am trying to figure out how the formula for the area of a trapezoid with exactly two parallel sides is deduced. In my textbook it says that the ...

solvemymaths.com/2015/03/07/proof-area-of-a-trapezium-trapezoid-us

Mar 7, 2015 ... At the Don Steward event last weekend, Don demonstrated how the formula for a trapezium can be derived in different ways. He asked the ...