-1-
-2-
DC/DA=sinx/sin(20).....(1)
DC/DB=sin(50)/sin(80)...(2) DA/DB=sin30/sin(x+40)....(3) من1،2،3 نجد sin(x+40)/sin(x)=sin(30)*sin(80)/sin(20)*sin(50) 1/tan(40)+1/tan(x)=sin(30)*sin(80)/sin(20)*sin(40)*sin(50) tan(x)=0.5771978866
x=30°
-3-
-4-