For a triangle
![ABC,](/media/m/8/a/f/8afcbd6e815ca10256c79a5b310e3d67.png)
let
![k](/media/m/f/1/3/f135be660b73381aa6bec048f0f79afc.png)
be its circumcircle with radius
![r.](/media/m/9/0/a/90a057247cc1f685a07aaac175675826.png)
The bisectors of the inner angles
![A, B,](/media/m/d/4/7/d47a5585e8b9ded795b817ac695beb7e.png)
and
![C](/media/m/5/a/b/5ab88f3f735b691e133767fe7ea0483c.png)
of the triangle intersect respectively the circle
![k](/media/m/f/1/3/f135be660b73381aa6bec048f0f79afc.png)
again at points
![A', B',](/media/m/3/8/c/38cc6337e51e5b59525fcb423d2e6165.png)
and
![C'.](/media/m/e/b/a/eba651ec35e7e3281026f4648e69ce7b.png)
Prove the inequality
![16Q^3 \geq 27 r^4 P,](/media/m/f/a/1/fa114c611bc25a3b3cd6ae4984832a04.png)
where
![Q](/media/m/4/5/c/45ce8d14aa1eb54f755fd8e332280abd.png)
and
![P](/media/m/9/6/8/968d210d037e7e95372de185e8fb8759.png)
are the areas of the triangles
![A'B'C'](/media/m/5/3/d/53d1d147ad89bd52a7038ce57a0957ef.png)
and
![ABC](/media/m/a/c/7/ac75dca5ddb22ad70f492e2e0a153f95.png)
respectively.
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For a triangle $ABC,$ let $k$ be its circumcircle with radius $r.$ The bisectors of the inner angles $A, B,$ and $C$ of the triangle intersect respectively the circle $k$ again at points $A', B',$ and $C'.$ Prove the inequality
$$16Q^3 \geq 27 r^4 P,$$
where $Q$ and $P$ are the areas of the triangles $A'B'C'$ and $ABC$ respectively.