Geometry classes, Problem 242. Triangle with Equilateral triangles, Parallelogram. Elearning.

Problem 242. Triangle with Equilateral triangles, Parallelogram

In the figure, equilateral triangles ABC', BCA', and ACB' are constructed on the sides of a triangle ABC. Prove that A'BC'B' is a parallelogram.
Post or view a solution. See also: Artwork of Problem 242

Elearn 242: Triangle with equilateral triangles

Problem 242 on Twitter:

If we build 3 equilateral triangles off the sides of ANY TRIANGLE, how can we explain the cameo appearance of this parallelogram? 🤔https://t.co/ENjFqXXa71 (Source: @gogeometry) @geogebra #MTBoS #ITeachMath #math #maths #geometry #proof #EdTech #MathChat #nctmslc19 pic.twitter.com/w3Im9ku9ht
— Tim Brzezinski (@Brzezinski_Math) October 17, 2019