第一題
不知道為什麼給那麼多東西，我只用
\(\displaystyle EH-HF=2 \)
\(\displaystyle EH+HF=k+2 \)
\(\displaystyle EH \times HF=4k \)
就解出\(\displaystyle EH=8,FH=6 \)
第二題
連接AD，
\(\displaystyle \angle{ADG}=\angle{OBF} \)
\(\displaystyle \angle{GAD}=\frac{1}{2}\widehat{CBD}=\angle{BOF} \)
故\(\displaystyle \Delta AGD \sim \Delta OFB \)
\(\displaystyle AG:AD=OF:OB=1:2 \)
\(\displaystyle AG=\frac{1}{2}AD=\frac{1}{2}AC \)
故\(\displaystyle AG=GC \)
