In Fig. 6.18, if LM∥CBLM \parallel CBLM∥CB and LN∥CDLN \parallel CDLN∥CD, prove that AMAN=ABAD=LMLN .\displaystyle \frac{AM}{AN} = \frac{AB}{AD} = \frac{LM}{LN}\,. ANAM=ADAB=LNLM.