Area of Square

Theorem: Area of a square is equal to the square of its side length.

Prerequisites:
Square (definition)
Area of rectangle (proof)

Proof:

Let ABCD be a square having side length equal to '$s$'. Since by definition, square is a special type of rectangle, hence using the formula for area of a rectangle, area of ABCD is:

$\qquad\quad\begin{align}\text{Area of ABCD} &= \text{(length)}\times\text{(breadth)}\\
&= s\times s\\
&= s^2\end{align}$

Q.E.D.


Recommended:
Area of triangle
Area of rectangle
characteristics of parallelogram