// calc tangent at x=a
public final void compute() {
if (!(f.isDefined() && P.isDefined() && deriv.isDefined())) {
tangent.setUndefined();
return;
}
// calc the tangent;
double a = P.inhomX;
double fa = f.evaluate(a);
double slope = deriv.evaluate(a);
tangent.setCoords(-slope, 1.0, a * slope - fa);
if (!pointOnFunction) T.setCoords(a, fa, 1.0);
}
// calc axes
@Override
public final void compute() {
// only parabola has directrix
if (c.type == GeoConicNDConstants.CONIC_PARABOLA) {
// directrix has direction of second eigenvector
// through point (b - p/2* eigenvec1)
directrix.x = -eigenvec[1].getY();
directrix.y = eigenvec[1].getX();
double px = b.getX() - c.p / 2.0 * eigenvec[0].getX();
double py = b.getY() - c.p / 2.0 * eigenvec[0].getY();
directrix.z = -(directrix.x * px + directrix.y * py);
P.setCoords(px, py, 1.0);
} else directrix.setUndefined();
}
public AlgoDirectrix(Construction cons, String label, GeoConic c) {
super(cons);
this.c = c;
eigenvec = c.eigenvec;
b = c.b;
directrix = new GeoLine(cons);
P = new GeoPoint(cons);
directrix.setStartPoint(P);
setInputOutput(); // for AlgoElement
compute();
directrix.setLabel(label);
}
public AlgoTangentFunctionPoint(Construction cons, GeoPoint2 P, GeoFunction f) {
super(cons);
this.P = P;
this.f = f;
tangent = new GeoLine(cons);
// check if P is defined as a point of the function's graph
pointOnFunction = false;
if (P.getParentAlgorithm() instanceof AlgoPointOnPath) {
AlgoPointOnPath algo = (AlgoPointOnPath) P.getParentAlgorithm();
pointOnFunction = algo.getPath() == f;
}
if (pointOnFunction) T = P;
else T = new GeoPoint2(cons);
tangent.setStartPoint(T);
// derivative of f
algoCAS = new AlgoDerivative(cons, f);
deriv = (GeoFunction) ((AlgoDerivative) algoCAS).getResult();
cons.removeFromConstructionList(algoCAS);
setInputOutput(); // for AlgoElement
compute();
}
/**
* Set the end point of the wrapped GeoLine
*
* @param point the new end point
*/
public static void setEndPoint(GeoLine geo, GeoPoint point) {
geo.setEndPoint(point);
}
/** @return the end point of the wrapped GeoLine */
public static GeoPoint getEndPoint(GeoLine geo) {
return geo.getEndPoint();
}
/** @return the start point of the wrapped geoLine */
public static GeoPoint getStartPoint(GeoLine geo) {
return geo.getStartPoint();
}
public AlgoTangentFunctionPoint(Construction cons, String label, GeoPoint2 P, GeoFunction f) {
this(cons, P, f);
tangent.setLabel(label);
}