Sin^2 a + cos( 60 градусов+а)*cos(60градусов-а)

Question

Sin^2 a + cos( 60 градусов+а)*cos(60градусов-а)

Answer 1

Sin^2 a + cos( 60+а)*cos(60-а)=sin^2 a + 0,5(cos( 60+а+60-а)+cos( 60+а-60+а))=
=sin^2 a + 0,5(cos120+cos2а)=sin^2 a + 0,5(-0,5+1-2sin^2 a)=sin^2 a + 0,25-sin^2 a=
=0,25