Trigonometry/Windows Scientific Calculator

On Windows 10, Click the Start Menu, type calculator and select Calculator.

The default is a standard calculator, which does not include trigonometry functions. Click the menu to the left of Standard, then click Scientific. There will now be options for sin, cos, and tan.

At the left side of the window, below the area where numbers are displayed but in the upper left of where the numbers and functions are entered, there is a button called DEG, RAD, or GRAD. Clicking this will allow you to switch between degrees, radians, and gradians.