let f, g, h, i be ExtReal; :: thesis: {f,g} /// {h,i} = {(f / h),(f / i),(g / h),(g / i)}
thus {f,g} /// {h,i} = {f,g} ** {(h "),(i ")} by Th27
.= {(f / h),(f / i),(g / h),(g / i)} by Th88 ; :: thesis: verum