[數撚圍爐區] Let ε < 0. (9)

中學讀過only

pish

it is an infinite dimensional space

小弟無記錯既話佢個班physics 友為左張Maxwell's equations 既magnetic field 果兩條equations generalize 到好似electric 咁可以有個potential 既gradient 咁take divergence 會變0，所以就用curl 黎define vector potential, i.e. A = curl v。base on this definition, div A =0, which is similar to electric potential case, which is div grad V = 0
sor for 1999
利申淨係UG 讀過下phys

Depends on choice of gauge