1988 AIME Problems/Problem 12
Let be an interior point of triangle and extend lines from the vertices through to the opposite sides. Let , , , and denote the lengths of the segments indicated in the figure. Find the product if and .
Call the cevians AD, BE, and CF. Using area ratios ( and have the same base), we have:
Similarily, and .
The identity is a form of Ceva's Theorem.
Plugging in , we get
Let be the weights of the respective vertices. We see that the weights of the feet of the cevians are . By mass points, we have that:
If we add the equations together, we get
If we multiply them together, we get
You can use mass points to derive Plugging it in yields We proceed as we did in Solution 1 - however, to make the equation look less messy, we do the substitution
Then we have Clearing fractions gives us Factoring yields and the left hand side looks suspiciously like what we want to find. (It is.)
Substituting yields our answer as
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