Unit triangular debt. Unit triangle is a mathematical concept, which was discovered by Leibniz, Germany. In line N, the common denominator (n+ 1) is put forward, which becomes a triangular table. This is a circulating debt, that is, the unit triangular debt. The unit triangle is characterized in that its unit fraction is a fraction with a numerator of 1 and a denominator of a positive integer, and its area is 1 square unit, which is called the unit regular triangle.