Hi Experts,

This is very strange: The book I am reading is doing some simple math with mistake? The load p(x) is applied at the surfaces of a crack (from 0 to a), the
released enagy
U = 0.5int[p(x)v(x,a)]dx (from 0 to a), fine.
However, the book then differentiate the equation with respect to a
and got
dU/da = 0.5int[p(x)dv(x,a)/da]dx (from 0 to a).
Is this forgot 'a' is a variable now in the integration! Why?

This is very strange: The book I am reading is doing some simple math with mistake? The load p(x) is applied at the surfaces of a crack (from 0 to a), the