Which construction is illustrated below?

The construction illustrated is the perpendicular of a line from a point not on the line.

EXAMPLE: Turning 4/3 into an improper fraction
In order to turn an improper fraction into a mixed fraction, you need to find the closest number to multiply the denominator by to get the numerator (ex: 3 times 1 is the closest number to 4). Then you would subtract that number after it was multiplied (in this case 1x3= 3) from the original numerator (so 4-3 = 1.) The answer for this question is 1 and 1/3.
Another example: 15/4 is 3 and 3/4 as a mixed number because 15 divided by 4 is closest to 3 (3x4 is 12 and 3x5 is 15, which is too large) with a remainder of 3. The closest multiple is the whole number and the remainder is the new numerator.
Hope this helps! I'm sorry if it's confusing-- it's easier to explain with paper and pencil :)