resolution wont go up to 1680x1050

i want to play gmod on my TV hooked up to my computer
the resolution is 1680x1050
gmod doesnt go up to that size
how do i set the resolution to what i want?

Click the “change aspect ratio” menu below the resolution menu and change it to “widescreen 16:10”.It will give you a set of 16:10 (which is what 1680x1050 is) ratio resolutions in the resolution menu.

yes but it doesnt show resolutions that high
only the lowest one