In the figure, equilateral triangles ABC', and BCA' are constructed on the sides AB and BC of a triangle ABC. Prove that AA' and CC' are congruent. View or post a solution.
  

Problem 241 on Twitter:

Build equilateral triangles off 2 sides of ANY TRIANGLE. How can we prove why this simply illustrated phenomenon always holds true? 🤔 https://t.co/uDDZJngWGU Source: @gogeometry. @geogebra #MTBoS #ITeachMath #math #maths #MathChat #geometry #proof #HSMath #EdTech #IowaMath19 pic.twitter.com/oakj9fS1ni

— Tim Brzezinski (@Brzezinski_Math) October 16, 2019