Refresher - Trigonometric Functions

For most purposes the three trig functions sine, cosine, and tangent are enough. There are, however, cases when some others are needed. In calculus, secant is frequently used. There are six ways of making ratios of two sides of a right triangle, and that gives the six functions:

$sin A = \frac{a}{c} = o p p / h y p$
$cos A = \frac{b}{c} = a d j / h y p$
$tan A = \frac{a}{b} = o p p / a d j = \frac{sin A}{cos A}$
$cot A = \frac{b}{a} = a d j / o p p = \frac{cos A}{sin A}$
$sec A = \frac{c}{b} = h y p / a d j = \frac{1}{cos A}$
$csc A = \frac{c}{a} = h y p / o p p = \frac{1}{sin A}$