

$$2p = B + b + 2S$$
Perimeter
$$A = \frac{\left(B + b \right) \times h}{2}$$
Area
$$B + b = \frac{2A}{h}$$
Sum of bases
$$h = \frac{2A}{B + b}$$
Height
$$B + b = 2p  2S$$
Sum of bases
$$S = \frac{2p  B  b}{2}$$
Oblique Side
$$p_{1} = \frac{ B  b }{2}$$
Oblique side Projection
$$B  b = 2 \times p_{1}$$
Difference of bases
$$B = b + 2p_{1}$$
Longer Base
$$b = B  2p_{1}$$
Shorter Base
Right Tr. delimited by height  oblique side
$$S = \sqrt{ {p_{1}}^2 + {h}^2 }$$
Side (Pythagoras' theorem)
$$h = \sqrt{ {S}^2  {p_{1}}^2 }$$
Height
$$p_{1} = \sqrt{ {S}^2  {h}^2 }$$
Oblique side Projection
Definition
An isosceles trapezoid is a trapezoid with oblique sides congruent.
Properties
 The oblique sides are congruent
 The angles adjacent to their respective bases are congruent
 Diagonals are congruent
 All the Generic Trapezoid formulas are valid
Isosceles Trapezoid Formulas
Data  Formula 

Perimeter  2p = B + b + 2 × S 
Area  A = [(B + b) × h] / 2 
Height  h = (2 × A) / (B + b) 
Oblique Side  S = (2p  B  b) / 2 
Oblique side Projection  p_{1} = (B  b) / 2 
Sum of bases  B + b = (2 × A) / h 
Sum of bases  B + b = 2p  2 × S 