which step in the construction of coping a lin segment ensures that the new line segment has the same length as the original line segment

Step-by-step explanation:

Now out of these points, i guess steps 5 and 6 are the main steps that ensure that the copied line segment is exactly the same as the original segment.

Here are the steps I think you probably will go through.

1. Draw a line that is longer than the segment but shorter than the width of the page.

1a. Make sure this line is  at least 1/2 inch from the left hand side.  

2. Use a compass to measure the length of the original segment. Never use a ruler. Rulers do not exist in pure geometry.

3. Measure out the distance on the line you just drew with the compass. One end is on the left hand edge and the other end (the pencil end) is marking the segment so it is the same length as the compass. You are done.

The key step either two or three.The steps to copy a line segment are given below:

1. Lets start with a line segment AB that we have to copy.

2. Now mark a point C. below or above AB, that will be one endpoint of the new line segment.

3. Now, put the compass tip on point A of the line segment AB.

4. Spread the compass up to point B, so as the compass width is equal to length of AB.

5. Without changing the compass width, now place the compass tip on the point C that you made in step 2.

6. Now, draw an arc roughly without changing the compass settings. Mark that point D. This will form the new line segment.

7. Draw a line from C to D.

Now out of these points, i guess steps 5 and 6 are the main steps that ensure that the copied line segment is exactly the same as the original segment.