和差化积
arcsin(根号(2/3))-pi/4=0.9553166181
pi-0.9553166181=2.186276036
0.9553166181-pi/4=0.1699184546
2.186276036-pi/4=1.400877873
x=0.1699184546+2kpi 或 1.400877873+2kpi
tanx+cosx=tan(0.1699184546)+cos(0.1699184546)=1.157171435 或
tanx+cosx=tan(1.400877873)+cos(1.400877873)=5.997529135