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December 1st, 2011, 04:32 AM   #1
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The triangle ABC has sides of length a,b and c.Show that perimeter of triangle ABC satisfies
p^2 = 2bc(1 + cos A) + 2ac(1 + cos B) + 2ab(1 + cos C)
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December 1st, 2011, 05:14 AM   #2
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Re: perimeter

The perimeter p is p = a + b + c. By the law of cosines, we may state:

Adding, we get:

Add 2ab + 2ac + 2bc to both sides:

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