## A History of the Progress of the Calculus of Variations During the Nineteenth Century |

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appears apply axis becomes Calculus of Variations chapter complete condition considered constant contains curve denote determined differential coefficients differential equation double integral dx dx dx dy dz dx dz dy dx dy dy dz dx dz dz equal example expression extends fact fixed formulæ function given gives Hence hold independent indicate integral involves Lagrange length limits manner maxima and minima maximum or minimum means memoir method minima values namely notation obtain occupies occur ordinary plane Poisson positive present problem proposed proved published quantities question refers relation remarks respect result Sarrus satisfied says second order shew solution Strauch suppose surface theorem theory third tion treatise vanish variable volume zero

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Page 140 - It is true that one of the fundamental principles of this method consists in removing as much as possible the differential coefficients of the variations which occur under the integral sign; but the calculus of variations only indicates this operation and refers the execution of it to the Integral Calculus. CHAPTER VI. DELAUNAY. 133. THE Academy of Sciences at Paris proposed the following as the subject of competition for their great mathematical prize in 1842 ; To find the limiting equations which...

Page 229 - Jacobi in 1837, and the memoir which Jacobi then published has given rise to an extensive series of commentaries and developments. Before however we proceed to Jacobi's investigations, we will give an analysis of Legendre's memoir and of some others connected with it. • 197. Legendre's memoir is entitled Memoire sur la maniere de distinguer les maxima des minima dans le Calcul des Variations.

Page 142 - ... can be calculated. It will be necessary to effect successive integrations, and to take each integral between appropriate limits, and these can be determined in the following manner. The order of the successive integrations being arbitrary, we can suppose that we integrate first with respect to z, then with respect to y, and then with respect to x. In the first integration y and x are regarded as constants, and the integration with respect to z extends over all the values of z which render f(x,...

Page 37 - ... of Variations involving the variation of a certain double integral, the limits of the integration being also variable; it is the earliest example of the solution of such a problem. Gauss himself says on page 67, " Sed quum calculus variationum integralium duplicium pro casu ubi etiam limites tanquam variabiles spectari debent, hactenus parum excultus sit, hanc disquisitionem subtilem paullo profundius petere oportet.

Page 345 - Bjorling discusses another particular example before considering the general equation, namely, among all surfaces which can be formed by the motion of a straight line which always remains parallel to a fixed plane, to determine that of minimum area.

Page 286 - Let there be any linear differential expression which involves x, y, and the differential coefficients of y with respect to x...

Page 409 - ... that y is then a minimum and so is F. These results do not agree with those in the book. The case in which y = k seems there overlooked. If y = k we have h = k = a. And it may be seen that the relation on the 14th line of page 165 of the book may be satisfied by supposing a = y and the angle CPY zero. 352. On page 365 the following problem is suggested ; to construct upon a given base a curve such that the superficial area of the surface generated by its revolution round AB may be given, and...