When you mean estimate do you mean by rounding the first numbers?
Greetings!
Yes, the degree on a monomial can be negative:
Example:

This is equal to:

Hope this helps.
-Benjamin
Sin 40° + sin 130° + sin 220° + sin 310° = ...
sin 130° = sin 50°;
sin 220° = - sin 40°;
sin 310° = - sin 50°
... = sin 40° + sin 50° - sin 40° - sin 50° = 0
Answer: 0.
Yes the equations are equivalent