1.fm+dn = the height of the bottom of BC (similarly).

2. connect AP BP CP. Similarly, the utilization area is equal to 0.5 times (AB*r3+BC*r 1+AC*r2)=0.5 times (BC*h). Because AB=AC=BC, R1+R2+R3 = H.

Our teacher said this question was not good, but did not specify which side of the polygon is high (for example, where is the height of the regular Pentagon? God knows) So r 1+R2+R3 = 2s divided by the side length (because all sides are equal).