A、ι×(1-ι4/(πR2I02))
B、ι×(1-ι3/(90R2I02))
C、ι×(1-ι5/(90R2I02))
D、ι×(1-ι4/(90R2I02))
A、ι×(1-ι4/(πR2I02))
B、ι×(1-ι3/(90R2I02))
C、ι×(1-ι5/(90R2I02))
D、ι×(1-ι4/(90R2I02))