Book I.  Propositions 11 and 12


Back to Propositions 11 and 12.

1.  Draw a straight line, choose a point on it, and at that point draw a
2.  perpendicular line.

2.  a)  In Proposition 11, what are we given?

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A straight line and a point on it.

2.  b)  What are we required to do?

To draw a straight line perpendicular to the given line, at the given point.

2.  c)  Practice Proposition 11.

3.  Use the indirect method to prove:  Only one line can be drawn
3.  perpendicular to a given line from a given point on it.

4.  To a straight line, and from a point not on it, drop a perpendicular
4.  line.

5.  a)  In Proposition 12, what are we given?

A straight line that may be made as long as we please, and a point not on it.

3.  b)  What are we required to do?

To draw a perpendicular to the given line, from the given point.

3.  c)  Practice Proposition 12.

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