这道题怎么做，请详细讲解一下---Here is the extraction of the content from the image: **Extraction Content:** **Question Stem:** 附加题。(共 10 分) 如图,在直角梯形 ABCD 中, AB=30 dm, ∠1=∠2=45°, ∠3=∠4=45°, 求梯形 ABCD 的 面积。 (Translation: Supplementary Problem. (Total 10 points) As shown in the figure, in right trapezoid ABCD, AB=30 dm, ∠1=∠2=45°, ∠3=∠4=45°, find the area of trapezoid ABCD.) **Provided Steps/Notes:** :∠1=∠2=45° :△AEBC 是等腰直角三角形 (Note: △AEBC is likely a typo, should be △EBC) :∠3=∠4=45° :△AED 是等腰直角三角形 [Partial line 1, mostly illegible text, appears to contain calculation or relationship] [Partial line 2, mostly illegible text, ends with what looks like "=30 (", followed by very smudged characters] S梯 = 30 x 30 ÷ 2 = 450 (cm²) (Note: The calculation uses dm units from the problem but outputs cm² unit) **Diagram Description:** * **Type:** Geometric figure, representing a quadrilateral labeled ABCD with internal lines. It visually appears to be a right trapezoid with its diagonals drawn. * **Shape:** A quadrilateral ABCD. Right angle symbols are indicated at vertices A and B. Based on standard representation of a trapezoid with these right angles, AB is likely the height, and AD and BC are the parallel bases. * **Vertices:** Labeled A, B, C, D, and E. A and B are positioned along the bottom. D is above and aligned with A, C is above and aligned with B. E is the intersection point of lines AC and BD, located inside the quadrilateral. * **Lines:** Sides AB, BC, CD, and DA. Diagonals AC and BD intersecting at E. * **Lengths:** The segment AB is labeled with the length "30". Another label "30" is below the segment AB. * **Angles:** * Right angle symbols are shown at vertices A and B. * Angle 1 (∠1) is labeled as "45" near vertex C, positioned to indicate angle ∠BCE. * Angle 2 (∠2) is labeled as "45" near point E, positioned to indicate angle ∠CEB. * Angle 3 (∠3) is labeled as "45" near vertex D, positioned to indicate angle ∠ADE. The numeral '3' is also labeled near D. * Angle 4 (∠4) is labeled as "45" near point E, positioned to indicate angle ∠AED. * **Annotations:** * Single tick mark is present on segments AD and AE, suggesting AD=AE. * Double tick mark is present on segments BC and BE, suggesting BC=BE. * **Relative Position:** E is the intersection of diagonals AC and BD. A, E, C are collinear. B, E, D are collinear.