grandes-ecoles 2012 QII.C.2

grandes-ecoles · France · centrale-maths1__mp Sequences and Series Convergence/Divergence Determination of Numerical Series
We define $$\varphi(x) = \begin{cases} \left(\frac{\sin x}{x}\right)^{2} & \text{if } x \neq 0 \\ 1 & \text{if } x = 0 \end{cases}$$ Justify that $\varphi \in L^{1}(\mathbb{R})$.
We define
$$\varphi(x) = \begin{cases} \left(\frac{\sin x}{x}\right)^{2} & \text{if } x \neq 0 \\ 1 & \text{if } x = 0 \end{cases}$$
Justify that $\varphi \in L^{1}(\mathbb{R})$.