Given some line segment AB, whose length you do not know, construct 
such that the length of 
is twice that of 
.
Steps of Construction-
1. Draw a line segment AB.
2. Keep the needle of compass on A and other end of it on B.
3. Draw point P. Put the needle of compass on P and draw an arc, naming it as R. Again draw an arc by putting the needle on R such that PR extends to Q.
4. Hence, PQ is the twice of AB.
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