[/quote]
,
be an acute triangle and let 
be an interior point for it such that 
.
When does equality hold?
be positive reals. Prove that there is a cyclic permutation 
of 
such that the inequality:![\[
\frac{a}{xa + yb + zc} + \frac{b}{xb + yc + za} + \frac{c}{xc + ya + zb} \geq \frac{3}{x + y + z}
\]](http://latex.artofproblemsolving.com/5/5/3/553527fc40a1b7d29dbdfb4b5e63635308f46c85.png)
and 
.
that satisfy the equation 
.
be a circle, and let a line 
intersect 
Circles 
and 
are internally tangent to 
and 
respectively, and both are tangent to 
Similarly, circles 
and 
are externally tangent to 
and 
respectively.
the segment 
has a length of 
and 
find the length of segment 
be real numbers such that 
.![\[
3 + (2 - \sqrt{3}) \cdot \frac{(b-c)^2}{b+(\sqrt{3}-1)c} \leq a+b+c
\]](http://latex.artofproblemsolving.com/5/a/8/5a83eaa7470bcca6546599ff4e296e4efec69b16.png)
and determine all the cases when the equality occurs.
have the same incenter 
.
is concyclic iff 
is concurrent
be the nonnegative integers in 
where 
.
.
.
such that 
where 
,
?
where 
,
be a scalene triangle with circumcircle 
and circumcircle 
.
and 
as the midpoints of 
and 
,
to 
.
meets 
,
intersects 
.
at 
and 
at 
.
intersect 
,
intersect 
.
is the reflection of 
and 
lies on the circumcircle of 
.
be real numbers such that 
and 
and determine the equality cases.
be positive real integer such that 
Prove that
such that 
and 
and 
Prove that
Y by
The measures of the three sides of an isosceles triangle are 
, and 
, respectively.
(i) Calculate its perimeter and area.
(ii) Is there an isosceles triangle with the same perimeter and same area, although the measurements of its sides are different from the previous triangle? If so, give all the correct isosceles triangles.
, and 
, respectively.(i) Calculate its perimeter and area.
(ii) Is there an isosceles triangle with the same perimeter and same area, although the measurements of its sides are different from the previous triangle? If so, give all the correct isosceles triangles.
.
.
.
.
.
See 
.
and 
the lengths of the sides of an isosceles triangle, 
and expanding, we obtain
,
,
,
.
and 
.
