Answer:
This is pythagoras
A squared plus b squared equals c squared.
The unknown side is c as its the hypotenuse,
So the length of the first side is 6.4 this squared = 40.96
The other length is 12 as 6 is the radius so the diameter of the circle amd therfore the length of the triangle is 12.
12 squared is 144
144 + 40.96 = 184.96
The length of c squared is 184.96
To find the length of c alone we calculate the square root.
The square root of 184.96 = 13.6
? = 13.6