### Home > CALC > Chapter 2 > Lesson 2.1.1 > Problem 2-11

2-11.

Expand and evaluate each of the following sums.

___ or, because of the symmetry of

, this problem can be simplified as:

Think about the symmetry of odd functions such as

.

Justify why the sum fromto will be .

Unfortunately,

does not have symmetry across the -axis. We have to expand and evaluate all terms.

_______

sin

is an odd function. Consider symmetry before evaluating.