设这个圆的半径是R.
则:PI*R^2+R+2*R=13.92
PI*R^2+3*R-13.92=0
R^2+3*R/PI-13.92/PI=0
R^2+0.95493*R-4.43087=0
R1=-0.477965+(0.477965^2+4.43087)^0.5=1.68cm
R2=-0.477965-(0.477965^2+4.43087)^0.5=-2.636cm(不取)
设这个圆的半径是1.68cm.
设这个圆的半径是R.
则:PI*R^2+R+2*R=13.92
PI*R^2+3*R-13.92=0
R^2+3*R/PI-13.92/PI=0
R^2+0.95493*R-4.43087=0
R1=-0.477965+(0.477965^2+4.43087)^0.5=1.68cm
R2=-0.477965-(0.477965^2+4.43087)^0.5=-2.636cm(不取)
设这个圆的半径是1.68cm.