me assume that stuf shood be
(1/2)*sine[(pi/2) +20] -2...and that angel be RADIANS
pi/2=1.5707963267948966192313216916397...
add 20 & get angel=21.570796.... rad
angel=21.57079632679489661923...radians
=1235.9155902616464175...deg
divide bi 360 & yu get 3.43309886183790671537767526745
leftover=0.433098861837906715377675267450
become 360*0.4339886... giv 155.9155902616464175 deg
or bout 156 deg
sine(156 deg)=0.40673664307580043
subtrakt 2 & yu get -1.5932633569241996