Difference between revisions of "1984 USAMO Problems/Problem 3"

(Solution)
(Solution)
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Greatest value is achieved when all the points are as close as possible to all being on a plane.
 
Greatest value is achieved when all the points are as close as possible to all being on a plane.
  
Since <math>\theta < \frac{\pi}{2}</math>, then  
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Since <math>\theta < \frac{\pi}{2}</math>, then <math>\angle APC + \angle BPD < \pi</math>
 
{{alternate solutions}}
 
{{alternate solutions}}
  

Revision as of 22:09, 12 November 2023

Problem

$P$, $A$, $B$, $C$, and $D$ are five distinct points in space such that $\angle APB = \angle BPC = \angle CPD = \angle DPA = \theta$, where $\theta$ is a given acute angle. Determine the greatest and least values of $\angle APC + \angle BPD$.

Solution

Greatest value is achieved when all the points are as close as possible to all being on a plane.

Since $\theta < \frac{\pi}{2}$, then $\angle APC + \angle BPD < \pi$ Alternate solutions are always welcome. If you have a different, elegant solution to this problem, please add it to this page.

See Also

1984 USAMO (ProblemsResources)
Preceded by
Problem 2
Followed by
Problem 4
1 2 3 4 5
All USAMO Problems and Solutions

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