**Trigonometric Functions**

There are six trigonometric functions: sine (sin), cosine (cos), tangent (tan), cotangent (cot), secant (sec) and cosecant (csc). The three major trigonometric functions (sin, cos, tan) each have their own keys. However, the three minor trigonometric functions must be calculated using their reciprocal definitions:

**Warning** .
The notation sin^{-1}(θ) represents the inverse sine function, not
the reciprocal of the sine function.

When
working with trigonometric functions, be sure the calculator is in the correct
Angle mode for your application. From a given screen, press **CTRL
SETUP** to access the mode menu. Highlight the Angle item. Then select
press the function key to select the angle measure appropriate for your application.

When working with a triangle or a geographical positioning system, use degree mode unless otherwise directed. When working with a graph or analytic trigonometry (e.g., solving a trigonometric equation), use radian mode unless otherwise directed. Most calculator errors in trigonometry occur because the calculator is in the wrong mode.

To
view the graph of a trigonometric function, enter the function in the equation
editor. For example, press **MENU 3** to access
the equation editor and enter Y1 = sin(X). To view the graph, press
**F5** to select DRAW. After the graph is drawn, then press **F2** to access
the zoom menu, select B:QUICK from the zoom menu, press the right arrow on the
thumb pad key to access the quick submenu, then press **2** to select 2:Trig.
The graph is redrawn with the horizontal tic marks placed at intervals of π/2.
Further, inappropriate vertical lines for asymptotes in the graph of the tangent
function, are not drawn.

For convenience, press **CTRL 0** to toggle
off and on the graph menu at the bottom of the screen.