formula

$\langle y, x \rangle = \sum_{k=1}^n y_{k} \overline{x_{k}} = \overline{\sum_{k=1}^n \overline{y_{k}} x_{k}} = \overline{\sum_{k=1}^n x_{k} \overline{y_{k}} } = \overline{\langle x, y \rangle}$