Direction Field

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Direction Field

 

a set of points in the xy-plane such that at each point a certain direction is defined. The direction is usually represented by an arrow passing through the point.

If the equation = f(x, y) is given, then at each point (x0, y0) of some region in the xy-plane the value of the slope k = f (x0, y0) of the tangent to the integral curve passing through this point is known, so that the direction of the tangent can be represented by an arrow. Thus the differential equation defines a direction field; conversely, a direction field in some region of the xy-plane defines a differential equation of the form = f(x, y). By sketching sufficiently many isoclines (curves joining points at which the direction field f (x, y) = C, C a constant, has the same value), we can obtain approximations to the integral curves, that is, curves having the prescribed directions as tangents (the isocline method).

Figure 1

Thedirection field of the equation = x2 + y2 is shown in Figure 1. The light curves (circles) represent isoclines, and the thicker curves represent integral curves.

REFERENCES

Stepanov, V. V. Kurs differentsial’nykh uravnenii, 8th ed. Moscow, 1959.
Petrovskii, I. G. Lektsii po teorii obyknovennykh differentsial’nykh uravnenii, 6th ed. Moscow, 1970.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Caption: Figure 3: Experimental results: (a) gray image of the horizontal specimen; (b) y direction field of the horizontal specimen; (c) gray image of vertical specimen; (d) y direction displacement field of the vertical specimen.
Order movement of rails and poles as direction field supposed to follow too obvious.
Still maintaining the direction field boundaries are on the right then left.
Figure 6 shows the direction field, the initial value, the solution, the first guess at a bounding box, and then finally the smaller sub-region required by the solution.

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