Choose a: 2+√ 2.
The bottom solution is shown in figure 1.
● Method 1: As shown in Figure 2, according to the oblique drawing method, the horizontally placed figure is a right-angled trapezoid. According to the meaning of the question, the upper bottom 1, the height 2, the lower bottom 1+√2, S=? ( 1+√2+ 1)×2=2+√2
● Method 2: S oblique = (√ 2/4) * S original.
The oblique sides are isosceles trapezoid. According to the known information, the upper bottom 1, the height √2/2, and the lower bottom √2+ 1.
S-skew =？ ( 1+√2+ 1)*√2/2=√2/2+ 1/2
∴S original = (√ 2/4) * s original = 2+√ 2
● Oblique two-sided drawing is to keep the length of the line segment parallel to the X axis unchanged, the line segment parallel to the Y axis becomes half of the original, and the area of oblique two-sided drawing is √2/4 times of the original graphic area.