1, in ordinary * * *: the product of two odd function is an even function; The product of two even functions is an even function; The product of even function and odd function is odd function.

2. The function image must be a curve in the coordinate system, but the curve in the coordinate system is not necessarily a function image.

3. The function image has at most one common point with the vertical axis, but it may not have any common point with the vertical axis.

4. If an even function is monotonic in the interval symmetrical about the origin, its monotonicity is just the opposite.

5. If odd function has monotonicity in the interval symmetrical about the origin, its monotonicity is exactly the same.