These symmetries are represented by <answer>functions</answer>. Each of these <answer>functions</answer> sends a point in the square to the corresponding point under the symmetry. For example, r1 sends a point to its rotation 90° clockwise around the square's center, and fh sends a point to its reflection across the square's vertical middle line. Composing two of these symmetry <answer>functions</answer> gives another symmetry function. These symmetries determine a group called the dihedral group of degree 4 and denoted D4. The underlying set of the group is the above set of symmetry <answer>functions</answer>, and the group operation is function composition. Two symmetries are combined by composing them as <answer>functions</answer>, that is, applying the first one to the square, and the second one to the result of the first application. The result of performing first a and then b is written symbolically from right to left as
What sends a point in the square to the relating point under the symmetry? 
functions