For a regular polygon, identify the center of the polygon
Draw a line from the center to the midpoint of any side
The length of that line is the apothem
If the side length and number of sides are known, use the formula: apothem = side length / (2 × tan(180° / number of sides))
If the area and perimeter are known, use the formula: apothem = 2 × area / perimeter
If the radius and number of sides are known, use trigonometric relationships to find the apothem
For a square, the apothem equals half the side length
For a regular hexagon, the apothem equals side length × √3 / 2