Question 734959
You just need the formula
If the endpoints are ( x1,y1)  and (x2,y2)
Then the distance between them is:
{{{ d = sqrt( ( x[2] - x[1] )^2 + ( y[2] - y[1] )^2 ) }}}
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It's important to understand that it doesn't really
matter which point you call (x1,y1) and (x2,y2)
( you can switch the 1's and 2's and the formula
will give you the same answer.
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If you knew the slope of the line segment and {{{ d }}},
and 1 of the endpoints, you could find the other endpoint.
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If you knew everything but one of the coordinates, like
x1, or x2, or y1, or y2, then you can find it.
Hope this helps