# Triple integral in the first octant

Calculus Level 4

What is the value of $\iiint_R \cos (x + y + z)\ dx\ dy\ dz$, where $R$ is the region bounded by $x \geq 0$, $y \geq 0$, $z \geq 0$ and $x + y + z \leq 2\pi$?

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