In a plane, two lines parallel to the same line are parallel to each other.
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____________________1/2_____________________ l
/
__________________3/4___________________ m
/
_____________________5/6______________________ n
/
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1. Line l is parallel to line m. 1. Given.
2. Line n is parallel to line m. 2. Given.
3. / 1 = / 3. 3. Corresponding angles are equal.
4. / 5 = / 3. 4. Corresponding angles are equal.
5. / 1 = / 5. 5. Substitution.
6. Line l is parallel to line n. 6. If corresponding angles are equal, then
the lines are parallel.