Question

please help me ,answer this question

Answer 1

$2 cos(5 \alpha ) sin(2 \alpha ) \\ 2 cos(7 \alpha + 3 \alpha \div 2) sin(7 \alpha - 3 \alpha \div 2) \\ 2 cos(c + d \div 2) sin(c - d \div 2) \\ sin(c) \: - \: sin(d) \\ sin(7 \alpha ) \: - \: sin(3 \alpha )$