If the radius of the inscribed circle of △ ABC is R and the perimeter of △ ABC is l, then the area of △ ABC is___ ．

If the radius of the inscribed circle of △ ABC is R and the perimeter of △ ABC is l, then the area of △ ABC is___ ．

As shown in the figure, connect OE, OD, of; OA, ob, OC; then OE ⊥ AB, of ⊥ AC, OD ⊥ BC; s △ ABC = 12ab × OE + 12bc × od + 12ac × of ∵ OE = of = od = R, AB + BC + AC = L, ∵ s △ ABC = 12ab × R + 12bc × R + 12ac × r = 12R (AB + BC + AC) = 12rl

Write out an algorithm for making ABC inscribed circle of triangle

r=2s/(a+b+c)

The radius of the inscribed circle of the triangle ABC is r, and the radius of the triangle ABC is r

The inscribed circle of a triangle is formed by
The intersection of the bisectors of two corners
The principle is that the distance from the point on the bisector to both sides of the angle is equal