Editing Subtangent (section)

==Definitions==
Let ''P''&nbsp;=&nbsp;(''x'',&nbsp;''y'') be a point on a given curve with ''A''&nbsp;=&nbsp;(''x'',&nbsp;0) its projection onto the ''x''-axis. Draw the tangent to the curve at ''P'' and let ''T'' be the point where this line intersects the ''x''-axis. Then ''TA'' is defined to be the '''subtangent''' at ''P''. Similarly, if normal to the curve at ''P'' intersects the ''x''-axis at ''N'' then ''AN'' is called the '''subnormal'''. In this context, the lengths ''PT'' and ''PN'' are called the '''tangent''' and '''normal''', not to be confused with the [[Tangent|tangent line]] and the normal line which are also called the tangent and normal.