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Chapter 1: Introduction to Geometry

Now you have the basic concepts of geometry, and the first and the most important use of these concepts are proofs. Proofs are the steps that are used to explain the relations between two geometric figures. Proofs are straightforward. All you have to do is to use a postulate or a theorem to justify the steps you use to express the relations between two geometric figures. I'm not going to cover every postulate and theorem. But I have a list of the most commonly used postulates and theorems, and I have provided a good sample of proof at below.

Given: QP is perpendicular to QR, angle 1 = angle 3
Prove: angle 3 + angle 2 = 90 degrees

 Statement Reason 1.  QP is perpendicular to QR 1.  Given 2.  Angle 1 + Angle 2 = 90 degrees 2.  If outer rays of two adj acute angles are perpendicular, then the sum of the angles is 90 3.  Angle 1 = Angle 3 3.  Given 4.  Angle 3 + Angle 2 = 90 degrees 4.  Substitution

This is all you have to know to get started on geometry. You should memorize these ideas so that you can use them readily later on. Please take a few minutes break and click here to continue to the next chapter. (You can also click on the drop-down list below to jump to any chapter you like.)

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