MathDB

Let

s=\frac{AB+BC+AC}{2}

be half-perimeter of triangle

ABC

. Let

L

and

N

be a point's on ray's

AB

and

CB

, for which

AL=CN=s

. Let

K

is point, symmetric of point

B

by circumcenter of

ABC

. Prove, that perpendicular from

K

NL

passes through incenter of

ABC

.
Solution for problem [url=http://www.artofproblemsolving.com/Forum/viewtopic.php?f=125&t=365714&p=2011659#p2011659]here

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