Assertion: right triangle's angle | /r/AtLocation | the perpendicular
Facets:
Source sentences:
text: In a letter to his former professor Michael Mästlin, he wrote, "If on a line which is divided in extreme and mean ratio one constructs a right angled triangle, such that the right angle is on the perpendicular put at the section point, then the smaller leg will equal the larger segment of the divided line.