[tex]\frac{c}{a}\text{ = }\frac{a}{r}[/tex]
Here, we want to compare triangles and such write the equivalent ratio on both
Mathematically, if two triangles are similar, the ratio of their sides are fixed
In the triangle consisting of c and a, we can see that c is the hypotenuse( the side facing the right-angle) while a represents the base
Now, in the triangle where we have a as the hypotenuse, we can see that the measure r reresents the base of the triangle
Thus, we can complete the proportion as;
[tex]\frac{c}{a}\text{ = }\frac{a}{r}[/tex]
