Step-by-step explanation:
Look at the picture.
We connect two congruent trapezoids as in the picture.
We created a parallelogram with a base length of b₁ + b₂ and a height h equal to the height of the trapezoid.
The formula of an area of a parallelogram:
[tex]A_p=(base)(height)\to A_p=(b_1+b_2)h[/tex]
The area of the trapezoid is half of the parallelogram area.
Therefore we have the formula of an area of trapezoid:
[tex]A_t=\dfrac{(b_1+b_2)h}{2}[/tex]
Therefore we need to be added the bases of a trapezoid.
