Question

Помогите решить пж хоть один пример. 1) cos79° cos34°-sin34° sin79° 2) cos(B+15°)-cosB×cos15 sinB×cos15° 3) cos(alpha+B)+sin alpha×sinB 4)cos (alpha-B)-sin alpha×sinB 5)sin5alpha×cos4alpha-cos5alpha×sin4alpha+sin alpha

Answer 1

1)cos79*cos34+sin79*sin34= cos(79-34)= cos45=0,5
2)(cosb*cos15-sinb*sin15-cosb*cos15)/(sinb*cos15)=(-sinb*sin15)/(sinb*cos15)=-sin15/cos15=-tg15