Question

Помогите, пожалуйста!

Answer 1

$1)\; \; 1+\underbrace {sin^212^\circ +cos12^\circ }_{1}=1+1=2\\\\2)\; \; 2\, sin12^\circ \cdot cos12^\circ =sin24^\circ \\\\3)\; \; \frac{tg12^\circ -tg10^\circ }{1+tg12^\circ \cdot tg10^\circ }=tg(12^\circ -10^\circ )=tg2^\circ \\\\4)\; \; cos50^\circ +cos40^\circ =2\, cos\frac{50^\circ +40^\circ }{2}\cdot cos\frac{50^\circ -40^\circ }{2}=2\, cos45^\circ \cdot cos5^\circ =\sqrt2\cdot cos5^\circ$