x²+y²=4
(x-r)²+y²=3
(x-r)²+(y-r)²=1
r(2x-r)=1,x=(1+r²)/2r
y=[√16r²-(1+r²)²]/2r
((1+r²)/2r-r)²+(√[16r²-(1+r²)²]/2r-r)²=1
(1-r²)²+(√[16r²-(1+r²)²]-4r²)²=4r²
√[16r²-(1+r²)²]=2r²+1
5r^4-10r²+2=0
r²=(10+√60)/10
r=√[(10+√60)/10]=1.77
(10+√60)/10=1+3+2√3cos∠BPC
cos∠BPC=(√20-10√3)/20
∠BPC=130º
简单分析一下,详情如图所示