Vejamos:
[tex]\left(sen(x)-cos(x)\right)^2=\left(\frac{1}{2}\right)^2 \\
\\
\left(sen(x)-cos(x)\right)^2=\left(\frac{1}{4}\right) \\
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sen^2(x)+cos^2(x)-2sen(x)cos(x)=1-2sen(x)cos(x)=\frac{1}{4} \\
\\
2sen(x)cos(x)=\frac{3}{4} \\
\\
sen(x)cos(x)=\frac{\frac{3}{4}}{2} \\
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sen(x)cos(x)=\frac{3}{8}[/tex]
