Trapezoid area with sides 6,15,16,20 equal to 163.926
where a and b are bases, h is height
where m is the middle line, h is the height
where d1,d2 are diagonals, α° is the angle between them
A trapezoid is a quadrilateral whose two sides are parallel (bases) and the other two are not parallel (sides).
Trapezoid area formula 
where a and b are the bases, c and d are the sides
where r is the radius of the inscribed circle, α° is the angle between the base and the sideSolution:
S =
a+b
2
·√c2 - ()2
(b-a)2+c2-d2
2·(b-a)
=
6+15
2
·√162 - ()2
(15-6)2+162-202
2·(15-6)
=
21
2
·√162 - ()2
92+162-202
2·9
=
21
2
·√256 - ()2
81+256-400
18
= 10.5
·√256 - ()2
-63
18
= 10.5
·√256 - (-3.5)2
= 10.5
·√256 - 12.25
= 10.5
·√243.75
= 10.5
·
15.612
=
163.926
Answer: trapezoid area with sides 6,15,16,20 equal to 163.926