The Basics of Trigonometry - 4.1

So what exactly is trigonometry?

Trigonometry is the measurement of triangles.
Well triangles have angles right? What are those you ask?

Angles are two rays with a common endpoint, which is called a vertex (plural--vertices). Every angle has an intial side, the starting position of the ray, and a terminal side, the position after rotation. Such an angle is in standard postion (see diagram to right). A positive angle is one that comes as a result of counterclockwise rotation. A Negative angle is one that results from clockwise rotation. Some of the angles that were discussed in class today are:

Acute - less than 90

Right - 90

Obtuse - greater than 90 but less than 180

Sraight - 180

Reflex - greater than 180

Complementary - (not to be confused with complimentary) - two angles whose sum is equal to 90

Supplementary - two angles whose sum is equal to 180

Since math always has to make things harder than they really need to be (just kidding Mr. Wilhelm...but not really), we no longer use degrees to measure angles; we use radians. But wait, what is a radian? One radian is the point at which the intercepted arc is equal to the radius of the circle. It can be represented by the simple equation s=r, where "s" is the intercepted arc and "r" is the radius.

Next, we talked about Coterminal Angles. Coterminal Angles are angles that have the same initial side and terminal side.

When changing from degrees to radians:

Multiply the degree measure by /180

When changing from radians to degrees:

Multiply the radian measure by 180/