Question

A)Sin(30+a)*cosa-cos(30+a)*sina. B)sin75

Answer 1

А)(sin30cosa+cos30sina)×cosa-(cos30cosa-sin30sina)×sina=sin30cos^2a+cos30sinacosa-cos30cosasina+sin30sin^2a=sin30cos^2a+sin30sin^2a=sin30 (cos^2a+sin^2a)=sin30=0,5

Answer 2

B)sin75=sin (30+45)=sin30cos45+cos30sin45=(1/2)×(√2/2)+( √3/2)×( √2/2) ( √2+ √6)/4