The triangle is a trigonometric arithmetic sequence with the circumference of 36 and the circumference of the inscribed circle of 6 π Calculate a side length of 12, inscribed circle radius of 3, then how to do

The triangle is a trigonometric arithmetic sequence with the circumference of 36 and the circumference of the inscribed circle of 6 π Calculate a side length of 12, inscribed circle radius of 3, then how to do

I think it's a right triangle. If the three sides form an arithmetic sequence, then the median side length is 12. There's no doubt about that. The circumference of the inscribed circle is 6 π, so the radius of the inscribed circle is 3. The circumference of the triangle is 36. The solution is as follows: suppose the long side is 12 + D, the short side is 12-d, and the half circumference of the triangle is p = 18