
54 Applied calculus of variations for engineers
and
y
− y + z =0.
The elimination of the Lagrange multiplier results in the system of
y − z + z
=0,
and
y
− y + z =0,
whose solution follows from classical calculus.
4.4 Linearization of second order problems
It is very common in engineering practice that the highest derivative of interest
is of second order. Accelerations in engineering analysis of motion, curvature
in description of space curves, and other important application concepts are
tied to the second derivative.
This specific case of quadratic problems may be reverted to a linear prob-
lem involving two functions. Consider
I(y)=
x
1
x
0
f(x, y, y
,y