Hi,
There are two ways to try:
You can define via a pure function
f = # Sin[#] &;
g = -Abs[#] &;
Here, # stands for x in the context or your example. Cap it off with an ampersand '&' when using this notation.
Which are evaluated as
In[23]:= f[\[Pi]]
Out[23]= 0
In[24]:= g[-10]
Out[24]= -10
And can be plotted by
Plot[{f[x], g[x]}, {x, 0, 2 \[Pi]}]
Or by
Clear[f, g];
f[x_] := x*Sin[x];
g[x_] := -Abs[x];
Which can be evaluated in the same way described above
Hope this helps.
Ben
