Get down with the lingo
Addition Formulas
Adding angles together is easy, unless they are already hanging out inside a trig function. Use the addition formulas to tease out the right result.
Amplitude
The height of the wave of a trigonometric function, or the distance between the midline and the maximum or minimum.
Cycle
The thing that repeats in a periodic function.
Coterminal Angles
Angles that start and end at the same spots (usually start at θ = 0). They are different in the direction they travel or how many times they go around. (e.g. 270° and -90°, 30° and 360°).
Double-angle Formulas
When trig functions hit the buffet table a second time, they use the double-angle formulas to find out how much weight they gained. Really, though, they're just the addition formulas with the same angle put in twice.
Even Function
f(-x) = f(x) Nothing gets an even function down.
Half-angle Formulas
Formulas used when there just isn't enough angle to go around.
Inverse Trigonometric Function
If we know the value of a trig function, we can use its inverse function to find the associated angle.
Midline
The line that runs between the maximum and minimum y-values of a trigonometric function; consider it the middle y-value.
Odd Function
f(-x) = -f(x) They can take a negative angle and blow it up into a negative function.
Period
The horizontal length of one complete cycle in the graph of a trigonometric function.