1) =sin(56+34)=sin 90= 1
cos 15= cos(45-30)= cos45*cos30+sin45sin30= √2/2*√3/2+√2/2*1/2=
=√6/4+√2/4= (√6+√2)/4
sin150*cos150= 1/2*(2sin150*cos150)=1/2sin300=1/2sin(270+30)=
=-1/2cos30=-1/2*√3/2=-√3/4
2) =sin²a+sin²acos²a-1)/cos²a= sin²acos²a-(1-sin²a)/cos²a=
=sin²a*cos²a-cos²a/cos²a= cos²a(sin²a-1)/cos²a=sin²a-1=-(1-sin²a)=-cos²a