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Evaluate the integral ${\displaystyle \underset{-\frac{}{18}}{\overset{\frac{}{18}}{}}}\frac{81cos(9)d}{1+(sin(9){)}^2}$

${\displaystyle \underset{-\frac{}{18}}{\overset{\frac{}{18}}{}}}\frac{81cos(9)d}{1+(sin(9){)}^2}=\frac{9}{2}$

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