Yes, that won't work. In Mathematica all functions start with a capital letter. Hence, sin needs to be Sin. Also the "e" is just a variable without any fixed value. If you mean the basis of the exponential function you will have to use E.
If you do not stick to the basic syntactic rules Mathematica will not evaluate.
IF you are not sure about how to type it in, you can also use "natural language input", i.e. you type a single "=" sign at the beginning of a line:
In many cases that fixes any syntactic errors.
Cheers,
Marco
Best wishes,
Marco
