Question

sin 420 градусов и tg 100 градусов.
Определите знак выражения .

Answer 1

$sin420^\circ =sin(360^\circ +60^\circ )=sin60^\circ \ \textgreater \ 0\\\\tg100^\circ =tg(180^\circ -80^\circ )=-tg80^\circ \ \textless \ 0\; \; \Rightarrow \\\\sin420^\circ \cdot tg100^\circ =-sin60^\circ \cdot tg80^\circ \ \textless \ 0$