We have shown that the angle sum of a triangle is . We have also shown that the measure of an inscribed angle is half the measure the central angle that intercepts the same arc. In this post, we use the Inscribed Angle Theorem to show that the Triangle Angle Sum Theorem holds. Theorem The […]

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# Posts tagged with 'angle sum theorem'

## The Proof of the Polygon Angle Sum Theorem

Introduction We have learned that the angle sum of a triangle is . We have also learned that the angle sum of a quadrilateral is . In getting the angle sum of quadrilaterals, we divided the quadrilateral into two triangles by drawing a diagonal. In this post, we use this method to find the angle […]

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## Proof of Angle Sum of Quadrilaterals

Introduction We have learned that the angle sum of a triangle is . What about the quadrilaterals? The square and the rectangles have four right angles, so clearly, the sum of their interior angles is . But what about other quadrilaterals? Before proceeding with the proof, to those who want to explore first, draw different […]

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