Euler's Equation/Independent of y'
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Theorem
Let $y$ be a mapping.
Let $J$ a functional be such that
- $\ds J \sqbrk y = \int_a^b \map F {x,y} \rd x$
Then the corresponding Euler's Equation can be reduced to:
- $F_y = 0$
Furthermore, this is an algebraic equation.
Proof
Assume that:
- $\ds J \sqbrk y = \int_a^b \map F {x,y} \rd x$
Then Euler's Equation for $J$ is:
- $F_y = 0$
Since $F$ is independent of $y'$, the equation is algebraic.
$\blacksquare$
Sources
- 1963: I.M. Gelfand and S.V. Fomin: Calculus of Variations ... (previous) ... (next): $\S 1.4$: The Simplest Variational Problem. Euler's Equation