When the triangle comes overlaid area rectangle to overlap a close fit. And then some to get an orange triangle-area overlay it will overlap a close fit, thus making the area a triangle is half the area of a rectangle.
When placed over a rectangular triangle is congruent fit. Then the excess will be placed over the orange triangles are congruent fit, the area of a triangle is half the area of a rectangle.
When the triangle cover the rectangular area will coincide. Then the excess is putting on the triangle area orange would be congruent fit the triangle is half the area of the area of a rectangle.