x^2 +y^2=164 is a serkel with senter at (0,0)
radius=root(164)=12.80624847
slope=4/5=0.8
me assume yu meen the tangent tu serkel hav that slope
take invers tangent(08.)=38.65980825 deg
hav 2 plaeses weer tangent equal this. 1 is 90deg+39.65980825 deg
other is 180deg beyond=180+39.66 deg=218.66 deg or -141.34 deg