4. Parallel Lines and Proportional Parts
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Recall the Triangle Midsegment Theorem and the Alternate Interior Angles Theorem.
57
We are given a diagram showing △KLM and its midsegments JH, JP, and PH. Let's find the value of x.
The Triangle Midsegment Theorem tells us that if a segment joins the midpoints of two sides of a triangle, then it is parallel to the third side of the triangle and its length is one-half the length of that side. Looking at the graph, we can note some parallel segments. JP ∥ LM JH ∥ KM PH ∥ KL According to the Alternate Interior Angles Theorem, since JH cuts the parallel segments JP and LM, then ∠ PJH and ∠ LHJ are congruent angles. Let's use this information to find x. m∠ PJH = m∠ LHJ ⇕ 57 ° = x ° Therefore, we found that x=57.