在直角 $△ABC$中， $CD$是斜边 $AB$上的高，则下列等式不成立的是

A．	${\left|\stackrel{\to }{AC}\right|}^2=\stackrel{\to }{AC·}\stackrel{\to }{AB}$	B．	${\left|\stackrel{\to }{BC}\right|}^2=\stackrel{\to }{BA}·\stackrel{\to }{BC}$
C．	${\left|AB\right|}^2=\stackrel{\to }{AC}·\stackrel{\to }{CD}$	D．	${\left|\stackrel{\to }{CD}\right|}^2=\frac{\left(\stackrel{\to }{AC·}\stackrel{\to }{AB}\right)\times (\stackrel{\to }{BA}·\stackrel{\to }{BC})}{{\left|\stackrel{\to }{AB}\right|}^2}$