CU-P-L1 Tangent at P

The Tangent at a point P on CU or the P-Tangent is the tangent at P to CU.

Construction

There is a simple construction:

1. Start with P and 2 random points P1,P2 on a cubic CU.
2. Draw line PP1 intersecting CU in S1.
3. Draw line PP2 intersecting CU in S2.
4. Draw line S1P2 intersecting CU in T2.
5. Draw line S2P1 intersecting CU in T1.

Let T be the 3^rd intersection point of T1T2 with CU.

T is the Tangential of P (CU-P-P1).

PT will be the Tangent at P to CU.

See also QPG#2111.

CU-P-L1 P-Tangent-00.fig

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