| __Math Forum - Ask Dr. Math__ *(Site not responding. Last check: 2007-11-07)* |

| | Date: Fri, 18 Aug 1995 17:24:28 +1000 From: Tony Snell Subject: Mathmatical proof, **cosine** rule G'day, I have been given this problem solving project. |

| | Prove that, in any triangle, the sum of the squares of two sides is equal to twice the square on half the third side plus twice the square on the line joining the midpoint of the third side to its opposite vertex (Hint: You may find the **cosine** rule useful). |

| | I know have to prove the left hand side equals the right hand side of the equation and use a variant of the **cosine** rule to prove the equation, but how? |

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