In the file I have attached, I have h(x) defined as h[x_]:=x^2 - 4x + 7cos[x] and I have tried to plot it and as you can see from the images, I get an empty graph. Why is this? And can someone help me fix it?
Cosine has to be spelled with t capitol "C". All built-in Mathematica functions start with a capitol.
when you define the function as
h[x_] := x^2 - 4 x + 7 Cos[x]
things work fine.