Question 960862
Second quadrant, so angle is between 90 and 180 degrees.  Make use of reference to Unit Circle based on cosine 15/17 and sine 8/17; the tangent function might be a good choice:


{{{arctan(8/15)}}} gives the simpler angle but what you really want would be
{{{highlight_green(180-arctan(8/15))}}}.


Not sure here about "exact value", but you have something about {{{180-28.07249=highlight(151.93*degrees)}}}.