dy (a) With x = z2 the chain rule gives dx Y(z) = y(2²), so the functional becomes S[Y] = 2 = 2 /² [² dz ² ( 12 (1²) ² z dz 0 rZ = = [² d= dz dy dz dy 1 dz dx dz dx/dz – w2y2 ( 1 y¹² - 12w²y²). The Euler-Lagrange equation is now d 'Y' dz Z which expands to zY" - Y' + 4z³w²Y = 0. = ) = + 4zw²Y = 0, 1 dy 2z dz where Z = X¹/2, " where How Come &

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
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X
Exercise 6.1 (R) The functional S[y] = f* dx (y¹² - w²y²), where w is a constant,
gives rise to the Euler-Lagrange equation y" +w²y = 0.
(a) Show that changing the independent variable to z where x = z² gives the functional
Z = √X,
S[Y]
=
Z
1
4x
dz
(Y' (2)² – 46²zY²),
Z
with the associated Euler-Lagrange equation
d²Y
dz²
Z
dy
dz
+4w²z³Y = 0.
Transcribed Image Text:X Exercise 6.1 (R) The functional S[y] = f* dx (y¹² - w²y²), where w is a constant, gives rise to the Euler-Lagrange equation y" +w²y = 0. (a) Show that changing the independent variable to z where x = z² gives the functional Z = √X, S[Y] = Z 1 4x dz (Y' (2)² – 46²zY²), Z with the associated Euler-Lagrange equation d²Y dz² Z dy dz +4w²z³Y = 0.
dy
dx
(a) With x = z2 the chain rule gives
Y(z) = y(z²), so the functional becomes
S[Y]:
=
2
Z
[² d
0
dz z
Z
1
-² [² d²
=
dz
1
42²
dy
dz
=
The Euler-Lagrange equation is now
2
dy dz
dz dx
-w²y²
( 1⁄y¹2² – 4zw²y²).
=
which expands to 2Y" - Y' + 4z³w²Y = 0.
dt (7) + 4zw²Y = 0,
dz
dy 1
dz dx/dz
=
1 dy
2z dz
where_Z = X¹/2,
where
How Come ??
Transcribed Image Text:dy dx (a) With x = z2 the chain rule gives Y(z) = y(z²), so the functional becomes S[Y]: = 2 Z [² d 0 dz z Z 1 -² [² d² = dz 1 42² dy dz = The Euler-Lagrange equation is now 2 dy dz dz dx -w²y² ( 1⁄y¹2² – 4zw²y²). = which expands to 2Y" - Y' + 4z³w²Y = 0. dt (7) + 4zw²Y = 0, dz dy 1 dz dx/dz = 1 dy 2z dz where_Z = X¹/2, where How Come ??
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