Proving Lines are Parallel

How do you know that the two lines will be parallel?

How do you know that lines g and h are parallel?

How do you know that lines f and h are parallel?

How do know that lines f and h will be parallel?

Using the image above, which two lines can you tell are NOT parallel? Why?

[math][/math]Using the image above, assuming angles 1, 9, and 17 are congruent, which lines ARE parallel?

What is the sign for parallel?

[math]\perp[/math] [math]\parallel[/math] [math]\cong[/math] [math]\equiv[/math] [math]\surd[/math] [math]\longleftrightarrow[/math] [math]\pi[/math]

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Information: Proving Lines are Parallel