<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><div class=""></div><div class=""><br class=""></div><div class="">On a N+1 point grid, we can use the chain rule to write the sensitivity to the derivative of the stress at a point j, τ’_j, as</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span></div></body></html>