MATLAB comes with two forms of documentation,
help command works in the Command Window; just enter
help followed by the name of a command.
>> help sin
You should see output like this:
sin Sine of argument in radians. sin(X) is the sine of the elements of X. See also asin, sind, sinpi.
Some documentation uses vocabulary we haven’t covered yet. For example,
the elements of X might not make sense until we get to vectors and matrices a few chapters from now.
doc pages are usually better. If you enter
doc sin, a browser window appears with more detailed information about the function, including examples of how to use it. The examples often use vectors and matrices, so they may not make sense yet, but you can get a preview of what’s coming.