Hey all, I was given a boundary value set of differential equations for the temperature profile and heat flux of a fin as a homework assignment. My professor showed us how to solve it using sbval in Mathcad. I put in the corresponding equations (right after the given variables). For the inital guess condition I was told to use the equation for q0 in the program. I have three parameters to examine which are the width of the fin, n [coefficient for heat transfer], and thermal conductivity for two different metals, respectively. For some reason, when I change the width from 1 to 5, the program tells me the values of sbval need to be real. I have no idea what that means or how to fix it. And I know it's not a unit issue because the given differential equations already are converted to be unitless so that doesn't have an effect on the issue. Some one please help!!!!!!!