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Complete the proof below that utilizes the Triangle Inequality Theorom.

Complete the proof below that utilizes the Triangle Inequality Theorom.-example-1
User Edem
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1 Answer

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1. Firstly, statement 1 is given in the question.


\bar{PL}\left|\right|\bar{MT}\text{ }\rightarrow\text{ 1. Given}

2. When two lines cut through two parallel lines, the alternate interior angles are congruent(equal)

So;


\measuredangle P\cong\measuredangle T\text{ }\rightarrow\text{ Alternate interior angles are equal}

3. Given

4. PK = KT

Since K is the mid point of PT as stated in the question, then PK will be of equal length as KT.


PK=KT\text{ }\rightarrow\text{ Since K is the midpoint of }\bar{PT}

5. Vertically opposite angles are equal.

So;


\measuredangle PKL=\measuredangle TKM\text{ }\rightarrow\text{ Vertical angles Theorem}

6. when two corresponding angles and the included side are respectively equal, a triangle is said to be congruent.


\Delta PKL\cong\Delta TKM\text{ }\rightarrow\text{ Congruent triangles (SAS- two sides and one including side are equal)}

7. The Triangle Inequality theorem states that the sum of two sides of a triangle is greater than the third side.


PK+KL>PL\text{ }\rightarrow\text{ Triangle Inequality Theorem}

8. CPCTC means that Corresponding Parts of Congruent Triangles are Congruent.

The corresponding sides of the two congruent triangles are;


\begin{gathered} \bar{KL}=\bar{KM} \\ \bar{PK}=\bar{KT} \\ \bar{PL}=\bar{MT} \end{gathered}

So;


\begin{gathered} \bar{KL}=\bar{KM}\text{ .} \\ \bar{PK}=\bar{KT}\text{ }\rightarrow\text{ CPCTC} \\ \bar{PL}=\bar{MT}\text{ .} \end{gathered}

9. The final one is a conbination of CPCTC and Triangle Inequality theorem


\bar{PK}+\bar{KM}>\bar{PL}\text{ }\rightarrow\text{ since }PK+KL>PL\text{ and }\bar{KL}=\bar{KM}

User Tetsuya Yamamoto
by
5.3k points
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