Trapezoid

Perimeter

Area

Midsegment

Spetial Trapezoids - Isosceles Trapezoids

- Tangent Quadrilateral

$$a+b=2c$$

Attention! Not all isosceles trapezoids are tangent quadrilaterals!

Area with the radius of the inscribed circle

$$s=\frac{a+b+2c}{4}$$

$$A=s·r$$

Spetial Trapezoids - Isosceles Trapezoids - Cyclic 

Quadrilateral

 

$$d^2=a·b+c^2$$

Attention! All isosceles trapezoids are also cyclic quadrilaterals!

Area with the radius of the circumscribed circle

$$A=\frac{d·c·\left(a+c\right)}{4R}$$