We have hitherto proceeded on the supposition that the given line was
small enough, and near enough, to be actually drawn on our paper of its
real size; as in the example given in Appendix I. We may, however, now
deduce a construction available under all circumstances, whatever may be
the distance and length of the line given.
[Illustration: Fig. 11.]
From Fig. 8. remove, for the sake of clearness, the lines _C′D′_, _bV_,
and _TV_; and, taking the figure as here in Fig. 11., draw from _a_, the
line _aR_ parallel to _AB_, cutting _BT_ in _R_.
Then _aR_ is to _AB_ as _aT_ is to _AT_.
---- ---- as _cT_ is to _CT_.
---- ---- as _TS_ is to _TD_.