Common Quadrilaterals
Square
![square.gif](/sites/default/files/users/Mathalino/plane-geometry/square.gif)
Area, $A = a^2$
Perimeter, $P = 4a$
Diagonal, $d = a\sqrt{2}$
Rectangle
![rectangle.gif](/sites/default/files/users/Mathalino/plane-geometry/rectangle.gif)
Area, $A = ab$
Perimeter, $P = 2(a + b)$
Diagonal, $d = \sqrt{a^2 + b^2}$
Rhombus
![rhombus.gif](/sites/default/files/users/Mathalino/plane-geometry/rhombus.gif)
Area, $A = a^2 \sin \theta = ah$
Perimeter, $P = 4a$
Shorter diagonal, $d_1 = a\sqrt{2 - 2 \cos \theta}$
longer diagonal, $d_2 = a\sqrt{2 + 2 \cos \theta}$
Note: The diagonals of square and rhombus are perpendicular to each other.
Parallelogram
![parallelogram.gif](/sites/default/files/users/Mathalino/plane-geometry/parallelogram.gif)
Area, $A = ab \sin \theta = ah$
Perimeter, $P = 2(a + b)$
Shorter diagonal, $d_1 = \sqrt{a^2 + b^2 - 2ab \cos \theta}$
Longer diagonal, $d_2 = \sqrt{a^2 + b^2 + 2ab \cos \theta}$
Trapezoid
![trapezoid.gif](/sites/default/files/users/Mathalino/plane-geometry/trapezoid.gif)
Area, $A = \frac{1}{2}(a + b)h$
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