Prove that in a triangle $\displaystyle a^2+b^2+c^2\le 9R^2$ where $\displaystyle a,\, b\, c$ are the lengths of the sides and $\displaystyle R$ is the radius of the circumcircle.
Drwa the diagram first and then solve the LHS first.
there will be 3 different triangles and take 2 at a time and since they will be congruent by SAS condition(side angle side) replace the a by the R by solving it further.....try it !!!!!!!!!!1