Question

Помогите пожалуйста:3

Answer 1

28.1.
а) sin40sin16=2sin28cos12
б) sin20-sin40=2sin10cos40
в) sin10sin50=2sin30cos20=cos20
г) sin52-sin36=2sin9cos44
28.2
а)cos15+cos45=2cos30cos15=√3 cos15
б) cos46-cos74=2sin120sin14
в) cos20+cos40=2cos30cos10=√3 cos10
г) cos75-cos15=-2sin45sin30=-√2/2
28.3
$a)sin frac{pi}{5}-sinfrac{pi}{10}=2sinfrac{pi}{20}cosfrac{3pi}{20}\b)sinfrac{pi}{3}+sinfrac{pi}{4}=2sinfrac{7pi}{24}cosfrac{pi}{24}\c)sinfrac{pi}{6}+sinfrac{pi}{7}=2sinfrac{13pi}{84}cosfrac{pi}{84}\d)sinfrac{pi}{3}-sinfrac{pi}{11}=2sinfrac{4pi}{33}cosfrac{7pi}{33}$