Secant (sec): is the reciprocal of cosine, i.e. the ratio of the length of the hypotenuse to the length of the adjacent side.
Important note: There is a big difference between sec θ and cos^{1}x. The first one means "1/cos θ". The second one involves finding an angle whose cosine is x. So on your calculator, don't use your cos^{1} button to find sec θ.
First find the length of the hypotenuse. Using the Pythagorean Theorem, or recognizing the Pythagorean Triple 51213, the length of the hypotenuse is 13.
