Isosceles trapezoid area

Question

I know that the area of any Isosceles trapezoid is: a+b/2 *h, but does anyone know how to prove this formula? I got this question as a math exercise and am now very stuck. Please help!

Answer 1

Since the parallel bases a, b of the Trapezoid share the height, and a trapezoid can be split into two triangles

of

(1/2)ah + (1/2)bh

If you factor out the common terms

(1/2)h(a + b)