I was solving an exercise on Isosceles trapezoid whose diagonal was given, and I note that If I draw a diagonal in the isosceles trapezoid I got two triangles
To determine the area of the triangles I draw their heights, which are perpendicular to the diagonal. The problem arises when I suppose that the sum of the height of the two triangles is equal to the diagonal. Funny thing I got the correct anwser doing that way, however it was only intuitive, not accurate.
But how to prove if $(a = b + c)$ is true or false ?