Below is right triangle CBA with the altitude of segment BD. Use the hide/show buttons to examine what is true about the three triangles, [math]\bigtriangleup CDB[/math], [math]\bigtriangleup BDA[/math], and [math]\bigtriangleup CBA[/math]. When you show each triangle, there will be a blue point (to move the triangle) and a red point (to rotate the triangle). [br][br][list=1][*]What do you notice is true about the three triangles? How did you determine this?[/*][*]In this image, the geometric mean would state [math]\frac{CD}{BD}=\frac{BD}{DA}[/math]. Using what you learned from the relationship among the triangles, why is this proportion true?[/*][/list]