perimeter of centers of tangent circles

Use the scroll bar in the applet to unfold the problem.[br]What happens when you move points M and N?[br][br]
ב1 עמוד 339 תרגיל 1
What is the relationship between the perimeter of the triangle[br] and the radius of the outer circle?
– Esther Gruenhut

Information: perimeter of centers of tangent circles