$\renewcommand{\Re}{\operatorname{Re}}$ $\renewcommand{\Im}{\operatorname{Im}}$ $\newcommand{\erf}{\operatorname{erf}}$ $\newcommand{\dag}{\dagger}$ $\newcommand{\const}{\mathrm{const}}$ $\newcommand{\arcsinh}{\operatorname{arcsinh}}$
Some of the problems could be solved based on the other problems and properties of Fourier transform (see Section 5.2) and such solutions are much shorter than from the scratch; seeing and exploiting connections is a plus.
Problem 1. Let $F$ be an operator of the unitary Fourier transform: $f(x)\to \hat{f}(k)$ with a factor $(2\pi)^{-1/2}$. Prove that
Problem 2. Let $\alpha>0$. Find Fourier transforms $\hat{f}(k)$ of functions
Problem 3. Let $\alpha>0$. Find Fourier transforms $\hat{f}(k)$ of functions
Problem 4. Let $\alpha>0$. Based on Fourier transform of $e^{-\alpha x^2/2}$ find Fourier transforms $\hat{f}(k)$ of functions
Problem 5. Let $a>0$. Find Fourier transforms $\hat{f}(k)$ of functions
$f(x)=\left\{\begin{aligned} & 1&& |x|\le a,\\ & 0 && |x|> a;\end{aligned}\right.$
$f(x)=\left\{\begin{aligned} & x && |x|\le a,\\ & 0 && |x|> a;\end{aligned}\right.$
$f(x)=\left\{\begin{aligned} & |x| && |x|\le a,\\ & 0 && |x|> a;\end{aligned}\right.$
$f(x)=\left\{\begin{aligned} & a-|x| && |x|\le a,\\ & 0 && |x|> a;\end{aligned}\right.$
$f(x)=\left\{\begin{aligned} & a^2-x^2 && |x|\le a,\\ & 0 && |x|> a;\end{aligned}\right.$
Using 1. calculate $\int_{-\infty}^\infty \frac{\sin (x)}{x}\,dx$.
Problem 6. Using Complex Variables class (if you took one) find directly Fourier transforms $\hat{f}(k)$ of functions
Problem 7.
Prove the same properties as in Problem 1 for multidimensional Fourier tramsform (see Subection 5.2.A).
Prove that $f$ if multidimensional function $f$ has a rotational symmetry (that means $f(Q\mathbf{x})= f(\mathbf{x})$ for all orthogonal transform $Q$) then $\hat{f}$ also has a rotational symmetry (and conversely).
Note. Equivalently $f$ has a rotational symmetry if $f(\mathbf{x})$depend only on $|\mathbf{x}|$.
Problem 8. Find multidimentional Fourier transforms $\hat{f}(\mathbf{k})$ of functions
$f(\mathbf{x})=\left\{\begin{aligned} & 1&& |\mathbf{x}|\le a,\\ & 0 && |\mathbf{x}|> a;\end{aligned}\right.$
$f(\mathbf{x})=\left\{\begin{aligned} &a-|\mathbf{x}| &&|\mathbf{x}|\le a,\\ &0 &&|\mathbf{x}|> a; \end{aligned}\right.$
$f(\mathbf{x})=\left\{\begin{aligned} &(a-|\mathbf{x}|)^2 &&|\mathbf{x}|\le a,\\ &0 &&|\mathbf{x}|> a; \end{aligned}\right.$
$f(\mathbf{x})=\left\{\begin{aligned} &a^2-|\mathbf{x}|^2 &&|\mathbf{x}|\le a,\\ &0 &&|\mathbf{x}|> a. \end{aligned}\right.$
$f(x)=e^{-\alpha |\mathbf{x}|}$;
$f(\mathbf{x})=|\mathbf{x}|e^{-\alpha |\mathbf{x}|}$;
$f(\mathbf{x})=|\mathbf{x}|^2e^{-\alpha |\mathbf{x}|}$.
Hint. Using Problem 6(b) observe that we need to find only $\hat{f}(0,\ldots,0, k)$ and use appropriate coordinate system (polar as $n=2$, or spherical as $n=3$ and so on).
Note. This problem could be solved as $n=2$, $n=3$ or $n\ge 2$ (any).