Common Quadrilaterals
Square

Area, A=a2
Perimeter, P=4a
Diagonal, d=a√2
Rectangle

Area, A=ab
Perimeter, P=2(a+b)
Diagonal, d=√a2+b2
Rhombus

Area, A=a2sinθ=ah
Perimeter, P=4a
Shorter diagonal, d1=a√2−2cosθ
longer diagonal, d2=a√2+2cosθ
Note: The diagonals of square and rhombus are perpendicular to each other.
Parallelogram

Area, A=absinθ=ah
Perimeter, P=2(a+b)
Shorter diagonal, d1=√a2+b2−2abcosθ
Longer diagonal, d2=√a2+b2+2abcosθ
Trapezoid

Area, A=12(a+b)h