# Deductive geometry - Similarity and congruence

• September 24th 2009, 05:15 AM
BG5965
Deductive geometry - Similarity and congruence

http://i301.photobucket.com/albums/n.../Noether11.png

Thanks so much to anyone who helps, I am certain this involves similarity and congruence.
• September 24th 2009, 06:58 AM
red_dog
We have $OE=2OD$.

But $OE=\frac{AC}{2}, \ OD=\frac{BC}{2}$.

Then $AC=2BC$.

Use Pitagora's theorem: $AC^2+BC^2=AB^2$.

Replace BC with $\frac{AC}{2}$ and AB with 10 and find AC.