Krishna
0

Step 1: Take the definition for the secant

            DEFINITION: The secant (sec) of an acute angle in a right triangle is a

            ratio. It is the length of the hypotenuse (hyp) divided by the length of    

            the adjacent leg (adj).

                                \frac{Hyp}{adj} or \frac{1}{\cos D}


Step 2: Substitute the relevant side lengths.

            EXAMPLE:  From triangle CBD

                                        Hyp = CD

                                        Adj to angle  D =BD

                                  \Rightarrow      \frac{CD}{BD}

                                       \Rightarrow      \frac{17}{8}