Given a non-degenerate triangle A B C with perimeter 16 with A 1 , B 1 and C 1 on B C , C A and A B such that A A 1 , B B 1 and C C 1 are medians.
What is the sum of the infimum and supremum values of A A 1 + B B 1 + C C 1 .
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
12 and 16 are attainable in the case of degenerate triangles, so all you need to from there is take the limit as a 'normal' triangle approximates a degenerate triangle.
For 16:
Consider the 'triangle' with side lengths 8 , 8 , 0
For 12:
Consider the 'triangle' with side lengths 4 , 4 , 8
So 12 and 16 are not attainable, but you can get arbitrarily close to these limits.
Log in to reply
wonderful Wen Z (+1), now the solution is complete and the problem and the answer is correct. That's what I wanted and was looking for. My apologies for Aditya (+1) and Sharky (+1). I'm going to delete my others comments...
Perfect solution! +1
Log in to reply
Another nice geometry problem of the day.
By the way, from which book you post these problems?
I don't have a good geometry book which has a lot of numerical problems to solve. Can you tell me other than GEOMETRY REVISITED ?
Log in to reply
Mathematics Olympiad Treasures
Log in to reply
@Sharky Kesa – That also i have. I want the book which contains numerical problems , meaning to find something instead of proving.
Do you solve only proving questions in geometry from these books?
Log in to reply
@Priyanshu Mishra – Yeah, mainly those since I practice from them for maths olympiads.
Problem Loading...
Note Loading...
Set Loading...
In the above triangle, using simple triangle inequality considering triangles, AGB, BGC, AGC we have,
⎩ ⎪ ⎨ ⎪ ⎧ 3 2 ( m a + m b ) > c 3 2 ( m a + m c ) > b 3 2 ( m c + m b ) > a
Adding we get , m a + m b + m c > 4 3 ( a + b + c ) = 1 2
Again by construction we claim that A D = D H and since B D = D C we have A B H C a parallelogram which says B H = A C
So in Δ ABH we have , 2 A D < A B + B H = A B + A C simillarly , 2 B E < B A + B C & 2 C F < A C + B C and adding we have ,
m a + m b + m c < ( a + b + c ) = 1 6 and thus 1 2 < A A 1 + B B 1 + C C 1 < 1 6 whch makes the answer 1 6 + 1 2 = 2 8
But to say these are not the max and min of the sum of medians as they would never attain this value whenever the triangle is non-degenerate. So in practical no such Extremum exists which it can attain, this is merely a upper and lower bound found till date which fits perfectly.