Partial Derivatives Product
**Problem:** Find the partial derivatives $\frac{\partial f}{\partial x}$ and $\frac{\partial f}{\partial y}$ for the function $f(x,y) = e^{xy} \sin(4y^2)$.
1. **Write down the function:**
$$f(x,y) = e^{xy} \sin(4y^2)$$
2. **Find $\frac{\partial f}{\partial x}$:**
Since $f$ is a product of two functions, treat $\sin(4y^2)$ as a constant with respect to $x$. The derivative of $e^{xy}$ with respect to $x$ is found using chain rule:
$$\frac{d}{dx} e^{xy} = e^{xy} \cdot y$$
Therefore,
$$\frac{\partial f}{\partial x} = y e^{xy} \sin(4y^2)$$
3. **Find $\frac{\partial f}{\partial y}$:**
Use the product rule since both factors depend on $y$:
$$\frac{\partial f}{\partial y} = \frac{\partial}{\partial y} \left(e^{xy} \right) \sin(4y^2) + e^{xy} \frac{\partial}{\partial y} \left( \sin(4y^2) \right)$$
Derivative of the first part:
$$\frac{\partial}{\partial y} e^{xy} = e^{xy} \cdot x$$
Derivative of the second part using chain rule:
$$\frac{\partial}{\partial y} \sin(4y^2) = \cos(4y^2) \cdot 8y$$
So,
$$\frac{\partial f}{\partial y} = x e^{xy} \sin(4y^2) + e^{xy} \cdot 8y \cos(4y^2)$$
**Final answers:**
$$\boxed{\frac{\partial f}{\partial x} = y e^{xy} \sin(4y^2)}$$
$$\boxed{\frac{\partial f}{\partial y} = x e^{xy} \sin(4y^2) + 8y e^{xy} \cos(4y^2)}$$