Similar triangles – measuring height with shadows

MathematicsPlane GeometryAges 13–14

Two similar triangles ABC and A'B'C' with ratio k: drag the vertices of ABC to reshape it, or drag B' or C' to change the ratio and rotate the second triangle — corresponding angles stay equal and the ratio of each pair of sides always equals k. In the application mode, the height of a tree is found from the shadows of the tree and of a person using two similar right triangles; drag the treetop or the tip of its shadow to change the values.