Question 891397
Let me avoid all the punctuation and subscript coding and just show your described equation as this:


{{{um=vp}}} using the variables in the same order as your description.  You want the argument inside of p.

{{{um/v=vp/v}}}
{{{p=um/v}}}
Since you want the input in p, you would want {{{arcsin(p)=arcsin(um/v)}}}.