Question 184463
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Opposite interior angles formed by a transversal that intersects two lines are equal if and only if the lines are parallel.


{{{drawing(
500,300,0,10,0,6,
line(1,2,9,2),
line(1,4,9,4),
line(2,1,8,5),
locate(3.2,2.5,A),
locate(4.7,2.5,B),
locate(5.5,3.8,C),
locate(7,3.8,D),
locate(.8,4,L[1]),
locate(.8,2,L[2])
)}}}



*[tex \Large \ \ \ \ \ \ \ \ \ \ \ \  L_1 \ \parallel\  L_2 \ \ \Leftrightarrow\ \ \angle A = \angle D\ \ \small\wedge\Large \ \ \angle B = \angle C]




John
*[tex \Large e^{i \pi} + 1 = 0]
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