Why can't the integral define the variable when its in a bound

This is a simple example of my problem. Why won’t it define “a” even though “a” only has one solution and should be able to be found? How can I rearrange it or what do I need to do to this equation to define “a”

I have this question because of lines 16 and 17 of this but the graph above better highlights the core of the problem

https://www.desmos.com/calculator/soxg18wvux?lang=en

implicit functions can only use x as a variable

You appear to have a lot of calculator-related questions. support.desmos.com is more specifically for those. This forum is more for Activity Builder questions, though there can be significant overlap. I’ve also found followers of the desmos subreddit are often better equipped to answer questions related to some of the limitations of the calculator regarding complex functions and graphs.

thank you I misunderstood what the point of this forum was