Here is the illustration of Brianchon Theorem:
Can you see why the following illustration is a ``particular case'' of this
theorem?
Given five straight lines,
show that they belong to a family of straight lines each tangent to a conic.
When an extra tangnet line is added,
where is the point of tangency?
From this, complete the problem ``Construct the conic tangent to five given
lines.''
Can you see why the following illustration is a ``particular case'' of
Brianchon theorem?
From this observation we see that the problem
``Construct the conic
tangent to four given lines and passing through a point contained in one of
the four given lines''
can be reduce to the problem
``Construct the
conic passing through three given points and tangent to two straight lines
each containing one of the three points.''
or even to the problem
``Construct the conic passing through four given points and tangent to a
straight line containing one of the four points.''
Can you see why the following illustration is a ``particular case'' of
Brianchon theorem?
How is this observation leads to the construction of a conic tangnet to three
given straight lines and passing through two points on two of them?
