What's the difference between directrix and parabola?

Directrix


Definition:

  • (n.) A directress.
  • (n.) A line along which a point in another line moves, or which in any way governs the motion of the point and determines the position of the curve generated by it; the line along which the generatrix moves in generating a surface.
  • (n.) A straight line so situated with respect to a conic section that the distance of any point of the curve from it has a constant ratio to the distance of the same point from the focus.

Example Sentences:

Parabola


Definition:

  • (n.) A kind of curve; one of the conic sections formed by the intersection of the surface of a cone with a plane parallel to one of its sides. It is a curve, any point of which is equally distant from a fixed point, called the focus, and a fixed straight line, called the directrix. See Focus.
  • (n.) One of a group of curves defined by the equation y = axn where n is a positive whole number or a positive fraction. For the cubical parabola n = 3; for the semicubical parabola n = /. See under Cubical, and Semicubical. The parabolas have infinite branches, but no rectilineal asymptotes.

Example Sentences:

  • (1) The major variation in these patterns can be modeled by families of parabolas with a single degree of freedom.
  • (2) The relation between concentration and absorption in an eight step calibration series is well described by a parabola of the 2nd degree.
  • (3) It was shown that the women used a parabola with a larger margin over the top of the hurdle than the men: A lower parabola would shorten the hurdle step, and would require the lengthening of the three interhurdle steps.
  • (4) Three to eight parabolas were averaged for subjects in each posture; the mean for each posture was calculated.
  • (5) It was found that the velocity profile of the FITC labelled RBC in straight microvessels was blunt as compared to a parabola.
  • (6) The "excitability ratio" is the first derivative of the response parabola and as such becomes a linear function of the actual arterial CO2 partial pressure.
  • (7) The equation of the resulting parabola, corresponding to the upper frontal arch, can be applied to every maxillary dimension.
  • (8) This increase is satisfactorily expressed by a cubic parabola.
  • (9) A not previously described relationship between HbA2 and total Hb was demonstrated and probably conformed to a second degree parabola.
  • (10) The shape of protrusive condyle path was like a section of parabola curved forward and downward.
  • (11) Evaluations of the arterial and venous bleeding were conducted at 3 rates x 3 parabolas, and capillary bleeding was evaluated with 5 parabolas x 2 methods (pig's foot and sponge).
  • (12) The flow velocity profile in the venule seems to deviate slightly from the Newtonian parabola.
  • (13) The concentration of factor VIIIa can be obtained from the quadratic coefficient of the equation describing the parabola.
  • (14) Pointing accuracy improved movement-to-movement but not parabola-to-parabola, indicating that prolonged exposure is needed for sustained adaptation.
  • (15) A "reference parabola" is introduced making the fluid pressure concept more understandable.
  • (16) Transcranial Doppler data with accompanying acceleration information were analyzed in three segments in each parabola.
  • (17) The following objectives are addressed in this study: 1) to discuss present techniques and two new radiographic measurement systems; 2) to establish mean, standard deviation, and normal range values for these measurement systems; 3) to determine if these measurements vary with foot size; and 4) to use the results to establish general guidelines for metatarsal parabola reconstruction.
  • (18) Reaction patterns of 90 cortical neurons to acetylcholine approximated by two parabolas have been divided on simple and complex.
  • (19) Each parabola included a period of 1.8 Gz, then approximately 20 seconds of weightlessness, and finally a period of 1.6 Gz; the cycle repeated almost immediately for the remainder of the set.
  • (20) The constant delta C model is explored and a physically more realistic model is advanced which allows for a temperature-dependent delta C which changes sign at some temperature within the range of stability of the native protein; delta G(T) then has the form of a skewed parabola.