Cos18.cos28+cos108.sin208/ sin34.sin146+sin236.sin304=
=cos18.cos28 + cos(90+18).sin(180+28)/
/sin34.sin(180-34)+ sin(270-34).sin(270+34)=
=cos18.cos28+(-cos72)(-sin28)/sin34.sin34+sin56.sin56=
=cos18.cos28+sin18.sin28/sin34.sin34 + sin56.sin56=
=cos(18+28)/sinˇ34+ cosˇ234= cos46/1 = cos46