Question

Помогите пожалуйста

Answer 1

$sin10^\circ \cdot cos20^\circ +cos10^\circ \cdot sin20^\circ =sin(10^\circ +20^\circ )=sin 30^\circ =\frac{1}{2}\\\\sin50^\circ \cdot cos5^\circ -cos50^\circ \cdot sin5^\circ =sin(50^\circ -5^\circ )=sin45^\circ =\frac{\sqrt2}{2}\\\\\\\star \; sin(a+b)=sina\cdot cosb+cosa\cdot sinb\; \; \star \\\\\star \; sin(a-b)=sina\cdot cosa-cosa\cdot sinb\; \; \star$