设DM长X厘米,BM长Y厘米.
√{5^2+[√(1^2+Y^2)]^2}=X
√[4^2+(4-Y)^2=X
26+Y^2=X^2
32+Y^2-8Y=X^2
8Y=6
BM=Y=3/4
DM=X=1.25√17
AM=4-Y=13/4
GM=√[1^2+(3/4)^2]=5/4
设DE为P厘米.
(5/4+P)[5-√(4^2-P^2)]÷2+P√(4^2-P^2)÷2+3/8=10
25/8-(5/8)√(4^2-P^2)+5P/2=77/8
-(5/8)√(4^2-P^2)+5P/2=13/2
5√(4^2-P^2)=20P-52
25(16-P^2)=400P+2704-2080P
400-25P^2=2704-1680P
P^2-67.2P+92.16=0
P=[67.2±√(4515.84-368.64)]÷2
=(67.2±64.4)/2
P1=65.8
P2=1.4
取P2.DE是1.4厘米.
不好意思,我习惯用繁琐复杂的方程.
写了1小时了,给点分吧.