### 11.7.7 Tangents to curves in the plane: tangent

See section 12.6.3 for tangents in space.

The tangent command takes as arguments either a curve and a point, or a
point defined with element (see section 11.6.14) using a curve and
parameter value.

tangent returns and draws the list of lines tangent to the
curve passing through the given point.

Input:

tangent(circle(0,1),1+i)

Output:

Input:

t := element(0..pi,pi/4):; A := element(circle(0,1),t):; tangent(A)

Output:

When tangent is called with an element,
the tangent will change along with the point on the element.