MathDB
pentagon with A=B=C=D=120

Source:

May 15, 2010
trigonometrygeometry unsolvedgeometry

Problem Statement

Let ABCDEABCDE be a pentagon with A^=B^=C^=D^=120∘\hat{A}=\hat{B}=\hat{C}=\hat{D}=120^{\circ}. Prove that 4⋅AC⋅BD≥3⋅AE⋅ED4\cdot AC \cdot BD\geq 3\cdot AE \cdot ED.
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