Sin36°+sin40°+sin44°+sin48°\2sin88°cos4°sin42°

Question

Sin36°+sin40°+sin44°+sin48°\2sin88°cos4°sin42°

Answer 1

(2sin42cos6+2sin42cos2)/(2sin88cos4sin42)=
=2sin42(cos6+cos2)/(2sin88cos4sin42)=
=2cos4cos2)(2sin88cos4sin42)=cos2/(cos2sin42)=1/sin42