May 13, 2007

Math World No.009

最近做了些IMO的考古題~
不過再來可能要到下禮拜才會繼續了~
先準備拿力學競賽的金牌吧~ ^^


(IMO 1959)
4. Construct a right triangle with given hypotenuse c such that the median drawn to the hypotenuse is the geometric mean of the two legs of the triangle.

5.
An arbitrary point M is selected in the interior of the segment AB. The square AMCD and MBEF are constructed on the same side of AB, with segments AM and MB as their respective bases. The circles circumscribed about these squares, with centers P and Q, intersect at M and also at another point N. Let N' denote the point of intersection of the straight lines AF and BC.
a) Prove that N and N' coincide;
b) Prove that the straight lines MN pass through a fixed point S independent of the choice of M;
c) Find the locus of the midpoints of the segments PQ as M varies between A and B.

※懶得翻譯了~ XDD

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