Найти множество значений функции: y=1/2sinxcosx-1

[latex] \frac{1}{4}*2sin(x)cos(x) -1= \frac{1}{4}sin(2x)-1 [/latex] [latex]-1 \leq sin(2x) \leq 1[/latex] [latex] -\frac{1}{4} \leq \frac{1}{4} sin(2x) \leq \frac{1}{4} [/latex] [latex]-\frac{1}{4}-1 \leq \frac{1}{4} sin(2x) -1\leq \frac{1}{4}-1[/latex] [latex]-\frac{5}{4} \leq \frac{1}{4} sin(2x)-1 \leq -\frac{3}{4}[/latex]