1. Given a digits {
} . Find the number of numbers of 6 digits which cantain
or
's digit and they is permulated (For example 137456 and 314756 is one numbers).
3. Given
is not isosceles triangle.
and
its incenter and circumcenter. The incircle tangents to
at a point
. The circumcircle of
intersects
at
. Prove that
, where
is radius of incircle of
.
5. Given points
and
lie a circle.
.
and
incenters of
.
midpoints of arcs
. Then prove that
are concurrent.
Πηγή: artofproblemsolving
Πηγή: artofproblemsolving
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