vei transforma unghiurile in unghiuri pentru care cunosti valorile functiilor trigonometrice
120=2*60
aplicam cos 2x=2cos^2x-1 si sin2x=2sinx*cosx
cos120=2cos^2(60)-1=2*1/4-1= -1/2
sin120=2sin60*cos60=2*1/2*rad3/2=rad3/2
tg120=sin120/cos120=(rad3/2) / (-1/2)= -rad3
ctg120=1/tg120= -1/rad3
135=180-45
cos135=cos180-45=cos180*cos45+sin180*sin45=-1*rad2/2+0*rad2/2=rad2/2
sin135=sin180-45=sin180*cos45-sin45*cos180=rad2/2
tg si ctg se calculeaza usor
150=180-30 si apoi calcule ca mai sus, tinand cont ca sin30=1/2 si cos30 =rad3/2
