Tag: theorem

Three proofs that the sum of angles of a triangle is 180

Theorem. The sum of the interior angles of any triangle is 180°. Here are three proofs for the sum of angles of triangles. Proof 1 uses the fact that the alternate interior angles formed by a transversal with two parallel lines are congruent. Proof 2 uses the exterior angle theorem. Proof 3 uses the idea…

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Area of an Equilateral Triangle

Somebody left this in my message box: Problem If a triangle is an equilateral triangle with 3m and you are not given the perpendicular length of a triangle, how do you calculate the area of a triangle? Obviously the sender know that the perpendicular length aka height or altitude of the triangle is needed to…

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