来自吕文红的问题
设Rt△ABC的各边长分别为a,b,c(斜边),⊙O为△ABC内切圆,运用切线长定理、面积等知识可得S△ABC=AE*BE
设Rt△ABC的各边长分别为a,b,c(斜边),⊙O为△ABC内切圆,运用切线长定理、面积等知识可得S△ABC=AE*BE
1回答
2020-10-13 03:38
设Rt△ABC的各边长分别为a,b,c(斜边),⊙O为△ABC内切圆,运用切线长定理、面积等知识可得S△ABC=AE*BE
设Rt△ABC的各边长分别为a,b,c(斜边),⊙O为△ABC内切圆,运用切线长定理、面积等知识可得S△ABC=AE*BE
记BC边切点为F,AC边切点为G,
S△ABC=ab/2=(AG+r)(BF+r)/2
=(AE+r)(BE+r)/2
=AE*BE/2+(AE+BE)r/2+r²/2
其中(AE+BE)r/2+r²/2=S△AGO+S△BFO+r²/2=(1/2)S△ABC,
故AE*BE/2=(1/2)S△ABC,即AE*BE=S△ABC