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# Formulas and Tables

Elementary Geometry

# Rectangle

Sides of a rectangle: $$a$$, $$b$$
Diagonal of a rectangle: $$d$$
Radius of the circumscribed circle: $$R$$

Perimeter of a rectangle: $$P$$
Area of a rectangle: $$S$$

1. A rectangle is a quadrilateral in which all four angles are right angles (equal to $$90^\circ$$).
1. Diagonal of a rectangle
$$d = \sqrt {{a^2} + {b^2}}$$
2. Radius of the circumscribed circle
$$R = d/2$$
3. Perimeter of a rectangle
$$P = 2\left( {a + b} \right)$$
4. Area of a rectangle
$$S = ab$$