Question

Найдите множество значений функции y=1-2cosx

Answer 1

$y = 1 - 2 \cos(x) \\ \cos(x) \in [ - 1;1] \\ 2 \cos(x) \in [ - 2;2] \\ - 2 \cos(x) \in [ - 2;2] \\ - 2 \cos(x) + 1 \in [ - 1;3] \rightarrow y \in [ - 1;3]$