Question

помогите с тригонометрией sin13°sin43°+sin47°cos13°

Answer 1

$sin13\cdot sin43+sin47\cdot cos13=sin13\cdot cos47+sin47\cdot cos13=\\\\=sin(13+47)=sin60=\frac{\sqrt3}{2}\\\\P.S.\; \; sin \alpha =cos(90- \alpha )\; \; \to \; \; sin43=cos47$