Question

(sin 75 ° cos 5 ° - cos 75 ° cos 85 °) : (cos 375 °cos 5° - sin 15° sin 365°) решить используя формулы приведения

Answer 1

(sin 75 ° cos 5 ° - cos 75 ° cos 85 °) : (cos 375 °cos 5° - sin 15° sin 365°)=
=(sin75cos5-cos75cos(90-5))/(cos(360+15)cos5-sin15sin(360+5))=
=(sin75cos5-cos75sin5)/(cos15cos5-sin15sin5)=sin70/cos20=
=sin(90-20)/cos20=cos20/cos20=1