Where P=(A+B+C)/2.

A, B, and C represent the side length of a triangle, and √ represents the root sign, that is, the numbers in the brackets immediately after it all have the root sign.

This problem uses Helen's formula, which is a formula for directly calculating the area of a triangle by using the side lengths of three sides of the triangle.

Compared with Helen's formula, Qin, a famous mathematician in China, put forward the "triclinic quadrature method" in Shu Shu Jiu Zhang. Qin called the three sides of a triangle small, medium and large. "Art" is the method.

Tridiagonal quadrature is to add a small diagonal to a large diagonal, send it to the diagonal, take half of the remainder after subtraction, multiply it by a large diagonal and send it to the one obtained above. After subtraction, the number obtained by dividing the remainder by Feng 4 is regarded as "real", and 1 is regarded as "angle". After squaring, you get the area.

References:

Baidu encyclopedia-tridiagonal quadrature