Question 985440
Another description of what you have:
Triangle made of the segments QR, RP, QR.
Internal angle measure at Q is 60 degrees.
QR is 4; PR=RP=3.5.


Law Of Sines will give you measures of the interior angles at R and P.  Either Law Of Sines or Law Of Cosines can be used to find measure of segment QP or PQ.


Just find one of the unknown angles using Law Of Sines, and the other unknown angle measure can be found through angle sum 180 for a triangle.  As one of the alternatives,  (actually the only way),  {{{sin(60)/3.5=sin(P)/4}}}.  Go from there.


If what you already say you found is correct, then you simply have
{{{60+81.79+R=180}}}
R being the measure at point R, the angle.