86. Calcule a integral definida de \( \int_{-\frac{\pi}{6}}^{\frac{\pi}{6}} \cos(3x) \, dx \). Resposta: \( \left[ \frac{\sin(3x)}{3} \right]_{-\f...

86. Calcule a integral definida de \( \int_{-\frac{\pi}{6}}^{\frac{\pi}{6}} \cos(3x) \, dx \).

Resposta: \( \left[ \frac{\sin(3x)}{3} \right]_{-\frac{\pi}{6}}^{\frac{\pi}{6}} = \frac{\sin(\frac{\pi}{2})}{3} - \frac{\sin(-\frac{\pi}{2})}{3} = \frac{1}{3} - \left(-\frac{1}{3}\right) = \frac{2}{3} \). Explicação: Aplique a regra fundamental do cálculo.