Consider
and
are the even functions.
From the definitions
and
.
Find the addition
.

.
If
and
are the even functions, then the addition
is an even function.
Consider
and
are the odd functions.
From the definitions
and
.
Find the addition
.

.
If
and
are the odd functions, then the addition
is an odd function.
Consider
is an even function and
is an odd function.
From the definitions
and
.
Find the addition
.

This is not equal to either
or
.
Thus,
is neither even nor odd function.
If
and
are the even functions, then the addition
is an even function.
If
and
are the odd functions, then the addition
is an odd function.
If one of the function is even and other is odd, then the addition
is neither even nor odd function.