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Problem
Problem
In a triangle
A
B
C
ABC
A
B
C
;
A
D
AD
A
D
,
B
E
BE
B
E
and
C
F
CF
C
F
are the altitudes and
R
R
R
is the circum radius, then the radius of the circle
D
E
F
DEF
D
E
F
is a.
2
R
2R
2
R
b.
R
R
R
c.
R
2
\frac{R}{2}
2
R
d. None of these
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