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 AnglesWhen 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 LinesSome of those oneofakind pairs of angles have the right to be used to check if currently really 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