Question

Найдите cos(a+b), если sina= 1/3 , cosa= -2 √2/3 , sinb= 0,2, cosb= 2 √6/5

Answer 1

сos(a+b)=-(8√3+1)/15
cos(a+b), если sina= 1/3 , cosa= -2 √2/3 , sinb= 0,2, cosb= 2 √6/5
сos(a+b)=cosacosb-sinasinb=-2√2/3*2 √6/5-1/3*0,2=-(8√3+1)/15