# Exact straight line by special square

- Author:
- asifsound

- Topic:
- Square

**■ If AB ≠ BC**Such case, we need 7 bars. ( cf. Exact straight line by general square. ) AB = BC condition causes the simplicity. (points A, C are shared by

**Green bars**.)

**■ AC // M'M is very important trick**In above sample, M is the middle point of CD. i.e. ratio is 0.5. But, any ratio is OK, of course. △CHA ∽ △MGM' --- so, HA // GM' --- so, HA // M'G'

**■ Imai's Low of cosines frame.**This tool is educational for students. I named this method

**"Imai's Low of cosines frame"**, as a memento. This method is simpler than

**"Hart's Inversor"**or

**"Hart's A-frame"**methods, I think so. But as a result, this tool is same as Hart's Inversor apparatus. That is, different approach, different proof.