Step 1: Recall the cosecant formula

            FORMULA: If θ is one of the acute angles in a triangle, then the cosecant of

            theta is the ratio of the  hypotenuse(hyp) to te opposite side(opp).

                     = \frac{hyp}{opp}

Step 2:  Plug in the relevant side lengths.

                 EXAMPLE: From triangle RTS

                        Opposite side to angle S = RT

                                   Hyp = RS

                                    ⇒ \frac{RS}{RT}

                                         ⇒ \frac{13}{12}