Difference between revisions of "2005 Canadian MO Problems/Problem 4"

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==Solution Outline==
 
==Solution Outline==
^hahahaha... you can probably use Ravi Sub. to finish the above.
 
 
OR
 
 
 
Use the formula <math>K=\dfrac{abc}{4R}</math> to get <math>KP/R^3=\dfrac{abc(a+b+c)}{4R^4}</math>.  Then use the extended sine law to get something in terms of sines, and use AM-GM and Jensen's to finish.  (Jensen's is used for <math>\sin A+\sin B+\sin C \le \dfrac{3\sqrt3}{2}</math>.
 
Use the formula <math>K=\dfrac{abc}{4R}</math> to get <math>KP/R^3=\dfrac{abc(a+b+c)}{4R^4}</math>.  Then use the extended sine law to get something in terms of sines, and use AM-GM and Jensen's to finish.  (Jensen's is used for <math>\sin A+\sin B+\sin C \le \dfrac{3\sqrt3}{2}</math>.

Latest revision as of 07:13, 1 November 2022

Problem

Let $ABC$ be a triangle with circumradius $R$, perimeter $P$ and area $K$. Determine the maximum value of $KP/R^3$.

Solution Outline

Use the formula $K=\dfrac{abc}{4R}$ to get $KP/R^3=\dfrac{abc(a+b+c)}{4R^4}$. Then use the extended sine law to get something in terms of sines, and use AM-GM and Jensen's to finish. (Jensen's is used for $\sin A+\sin B+\sin C \le \dfrac{3\sqrt3}{2}$.