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Published byMeghan Haynes Modified over 9 years ago
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2-5 PROVING ANGLES CONGRUENT Objective: to prove and apply theorems about angles
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Remember… A postulate is an accepted statement of fact. A theorem is a conjecture that is proven. What is the difference between the two? You do not have to prove a postulate. You do have to prove a theorem. Let’s look at some theorems, and see how we can prove them…
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Vertical Angles Theorem One way we can prove a theorem is by using a paragraph proof, in which we literally write the proof out as sentences in a paragraph. LET’S SEE THIS IN ACTION!!!
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Proof of Vertical Angles Theorem
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Ex 1: Using Vertical Angle Theorem Example 1: Find the value of x. Then find the measure of each angle.
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You Try… You try. Find the value of x. Then find the measure of each angle.
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Try another… Find the values of x and y.
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Congruent Supplements Theorem In this example, x and y are both supplements of 50. Therefore,. Solve and you’ll see! The angles do not have to be vertical angles for this theorem to hold true. Look….
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Other useful theorems:
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