Some notes about symbols used in trigonometry

Trigonometry is very closely connected to the geometry of triangles, so we will use illustrations like the one above on a regular basis.  Because there are so many different things to consider, we use different alphabets to signify different types of objects.

The standard way to discuss this particular triangle is to call it triangle ABC, where the capital letters in the English alphabet refer to the points.  (A point may also be called a vertex.  The plural is vertices.)  The sides are designated by lowercase English alphabet letters. The side opposite a lettered vertex will share the same letter, only in lowercase.  In this example, side a is opposite point A, side b is opposite point B and side c is opposite point C.

Angles are yet another different object and they are designated with Greek letters.  This blog's editing software is based on HTML, which doesn't have the Greek alphabet symbols readily available, so I will have to type out the words alpha, beta and gamma when referring to angles here.  On any other printed material, the actual Greek letters will be used.  As you can see in this picture, the angle at point A is alpha, the angle at point B is beta and the angle at point C is gamma.

We don't use all the Greek letters angle designations.  One obvious example is pi, which is the Greek letter for p in English and is already being used to mean 3.14159..., the ratio of the circumference of a circle to its diameter.  Besides alpha, beta and gamma, the most common Greek letters used in trigonometry are delta, which looks like a squiggly lowercase d, and  theta,  which looks like the letter o with a horizontal line crossing in the middle.