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February 28th, 2018, 03:14 AM   #1
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Trigonometry and a Convex Quadrilateral


I'm stuck in another math problem...

sin A + sin B + sin C + sin D = 4 * sin(A+B)/2 * sin(B+C)/2 * sin(C+A)/2

"prove in a convex square ABCD the formula above"


Last edited by greg1313; February 28th, 2018 at 07:27 PM.
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February 28th, 2018, 04:53 PM   #2
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What is a convex square?
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March 1st, 2018, 01:55 AM   #3
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It's reasonable to assume that "convex square" should be "convex quadrilateral". The given equation will hold if sin(A + B + C) = sin(D). This is easy to prove by use of these identities and the fact that the internal angles of a convex quadrilateral sum to 360°.
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