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Finland Contests
Finnish National High School Mathematics Competition
2011 Finnish National High School Mathematics Competition
3
3
Part of
2011 Finnish National High School Mathematics Competition
Problems
(1)
In isosceles ABC, angle BAD < angle DAE
Source: Finland 2011, Problem 3
5/5/2013
Points
D
D
D
and
E
E
E
divides the base
B
C
BC
BC
of an isosceles triangle
A
B
C
ABC
A
BC
into three equal parts and
D
D
D
is between
B
B
B
and
E
.
E.
E
.
Show that
∠
B
A
D
<
∠
D
A
E
.
\angle BAD<\angle DAE.
∠
B
A
D
<
∠
D
A
E
.
trigonometry
geometry
symmetry
trig identities
Law of Sines
geometry unsolved