Step 1: Recall the formula of cosine

             FORMULA: The cosine (cos) of an angle in a right triangle is a ratio. It is

                                 the length of the adjacentleg (adj) divided by the length of  

                                 the hypotenuse (hyp).

Step 2: Substitute the appropriate side lengths in the formula.

            EXAMPLE: From triangle UVT

                                Adjacent leg to angle U = UV

                                           Hyp = UT

                          \Rightarrow   \frac{UV}{UT}

                          \Rightarrow   \frac{45}{53}