Let $\triangle ABC$ inscribed in circle with center $O$ and radius $r$. Let $D,E,F$ be the mid-point of side $BC,CA,AB,$ respectively then $OD,OE,OF$ meet the circumcircle at $L,M,N$ respectively. If $DL=a, EM=b, FN=c$ then find the area of the triangle in term of $r,a,b,c$
Could someone help me with this? I approach using Pythagorean to find radius but end up with everything just equal to each other as it should be.