Parallel Lines

Lines room parallel if they are always the very same distance personal (called "equidistant"), and will never ever meet. Just remember:

Always the very same distance apart and also never touching.

You are watching: Do parallel lines have to be the same length

The red heat is parallel come the blue heat in each of this examples:


Try that yourself:

Pairs of Angles


When parallel lines get crossed by one more line (which is called a Transversal), you have the right to see that countless angles are the same, together in this example:

These angles deserve to be made right into pairs the angles which have special names.

Click top top each surname to check out it highlighted:

Now play v it here. Shot dragging the points, and choosing various angle types. Girlfriend can likewise turn "Parallel" turn off or on:

Testing because that Parallel Lines

Some of those one-of-a-kind pairs of angles have the right to be used to check if currently really space parallel:
If any type of Pair the ...

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Corresponding Angles room equala = e
Alternate interior Angles are equalc = f
Alternate Exterior Angles are equalb = g
Consecutive inner Angles add up come 180°d + f = 180°
... Climate the lines space Parallel
These currently are parallel, since a pair of equivalent Angles space equal.
These lines space not parallel, because a pair that Consecutive internal Angles perform not add up to 180° (81° + 101° =182°)
These currently are parallel, because a pair of alternate Interior Angles space equal

angles On a directly Line Angles roughly a suggest Transversal Congruent angles Vertical angle Geometry index