Angles are applied in two primary modes: degrees and radians. Set the mode accordingly.
Warning: most calculator errors in trigonometry occur because the calculator is in the wrong mode.
To set the angle mode, press . Then navigate to the third line in the mode menu and select (highlight, then press ) either Radian or Degree mode. Press QUIT (located above the MODE key) to return to the home screen.
Degree Mode
In degree mode, angles can be entered as decimal degrees (DD) or degressminutesseconds (DMS).
For example, to evaluate tan(17°43'25"), press
TAN ANGLE (located above MATRX) ANGLE " (located above +) 
While in degree mode, you can convert radians to degrees. For example, to convert 1.23 radians to degrees, press

Hence, 1.23'70.4738088°.
Radian Mode
Set the calculator to RADIAN mode. Radian angles can then be entered as ordinary numbers. For example, to evaluate
, press
SIN Hence, .707107. 
From either mode, convert degrees to radians as follows. Enter the angle using the DMS symbols from the angle menu, convert to decimal degrees, then multiply by . For example, to convert 17°43'25" to radians, press
ANGLE
(to select 1:°) ANGLE (to select 2:' ) " (located above +) ANS (located above the key) . [Hence, 17°43'25" .31 radians.] 