Question

The projection of a line segment AB on another line is the line segment CD, then IABl = lCDl.
True or false with full explanation

Answer 1

Let consider any line segment $AB$ with $|AB|=1.$ The projection of a line segment $AB$ on another line is the line segment $CD$ formed by the projections of the end points of the line segment $AB$ on this line. If we choose such a line $l$ that the segment $AB$ is perpendicular to $l$, then the points A and B projects on the same point $C=D$ of the line $l$, and therefore, $|CD|=0$.

Answer: false