Use the buttons in the app below to explore the construction step by step and find out an unexpected result![br][br]Can you prove this property?

You can actually prove this result in different ways. [br]One way could be by using triangles metric properties, so trigonometry rules, but it involves a lot of calculations.[br][br]Here we will focus on the geometric properties of the objects and geometric transformations.[br]Use the slider in the app below and observe what happens.[br][br]Think about the formula you use to calculate the area of a triangle, and consider the elements of each rotated triangle that are congruent to the ones of the given triangle.

[size=85]Inspired by the Nrich activity "Surprising Equalities".[/size]