TeX source:
\begin{array}{rcl}\mathbb{D} &=& \mathbb{R}\times\mathbb{R}\times\mathbb{R} \\\\f(x,y,z) &=& \dfrac{\pi x\sin\left(7y^5\right)}{e^{10xz+1}} \\&=& \pi x\sin\left(7y^5\right)e^{-(10xz+1)} \\&=& \pi x\sin\left(7y^5\right)e^{-10xz-1}\end{array}