I assume you are using a TI-83/TI-84 series calculator.
To switch between radian and degree mode, press the "MODE" button to get into the mode menu. Then scroll down to the line that reads "RADIAN DEGREE". Since you are switching from the default of "RADIAN", just move the cursor over to highlight "DEGREE" and press "ENTER" to select it. Then press "2nd" and "QUIT" to get out of the mode menu.