\frac{1}{t_{p}} - \frac{1}{t_{s}} = \frac{1}{t_{1}}, \frac{1}{t_{p}} + \frac{1}{t_{s}} = \frac{1}{t_{s}}

${\frac{1}{t_p} - \frac{1}{t_s} = \frac{1}{t_1}\quad,\quad \frac{1}{t_p} + \frac{1}{t_s} = \frac{1}{t_s}}$