Tìm GTLN và GTNN

G

girlbuon10594

[TEX]sin\alpha.cos\alpha=\frac{1}{2}sin2\alpha[/TEX]

[TEX]sin2\alpha\in[-1;1][/TEX]
\Leftrightarrow [TEX]\frac{-1}{2} \leq \frac{1}{2}sin2\alpha \leq \frac{1}{2}[/TEX]
Hay: [TEX]\frac{-1}{2}\leq sin\alpha.cos\alpha \leq\frac{1}{2}[/TEX]
\Rightarrow [TEX]Max=\frac{1}{2}[/TEX]
[TEX]Min=\frac{-1}{2}[/TEX]
 
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