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3
Trigonometric inequality
Trigonometric inequality
Source: IMOTC 2015 Practice Test 1 Problem 3
July 11, 2015
trigonometry
inequalities
Problem Statement
Prove that for any triangle
A
B
C
ABC
A
BC
, the inequality
∑
cyclic
cos
A
≤
∑
cyclic
sin
(
A
/
2
)
\displaystyle\sum_{\text{cyclic}}\cos A\le\sum_{\text{cyclic}}\sin (A/2)
cyclic
∑
cos
A
≤
cyclic
∑
sin
(
A
/2
)
holds.
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