Sin36°+sin40°+sin44°+sin48°\2sin88°cos4°sin42°
(2sin42cos6+2sin42cos2)/(2sin88cos4sin42)= =2sin42(cos6+cos2)/(2sin88cos4sin42)= =2cos4cos2)(2sin88cos4sin42)=cos2/(cos2sin42)=1/sin42