这个题目怎么做，使用中文解答---**Question 23 (Total points: 12)** **Problem Description:** As shown in the figure, AB is the diameter of semicircle O. Point F is on the semicircle. Point P is on the extension line of AB. PC is tangent to the semicircle at point C. The extension line of OF intersects PC at point D. AC intersects OF at point E. DC = DE. **(1) Write down one angle in the figure that is equal to ∠DEC: _________ ;** **(2) Prove: OD ⊥ AB;** **(3) If OA = 2OE, DF = 2, find the length of PB.** **Diagram Description:** * Type: Geometric Figure. * Main Elements: * A semicircle with center O and diameter AB. * Points A, O, B are collinear, with O between A and B. P is on the line extending AB beyond B. * Points F and C are on the arc of the semicircle. * Lines: AB (diameter), OF (radius), OF extended to D, AC (chord), PC (line tangent to the semicircle at C), DC. * Intersections: OF intersects AC at E. The extension of OF intersects PC at D. * Labels: Points are labeled A, B, O, P, F, C, D, E. The problem number "(第 23 题)" is shown below the diagram. * Relative Position and Direction: O is the center of the semicircle. AB is a horizontal line segment. The semicircle is above AB. P is to the right of B on the extension of AB. F and C are on the curve of the semicircle. OF is a radius. PC touches the semicircle at C. AC is a line segment inside the semicircle. OF and AC intersect inside the semicircle at E. D is on the line going through O and F, outside the semicircle. D is also on the tangent line PC. **Given Conditions in Text:** * AB is the diameter of semicircle O. * F is on the semicircle. * P is on the extension line of AB. * PC is tangent to the semicircle at C. * The extension line of OF intersects PC at D. * AC intersects OF at E. * DC = DE. * In part (3): OA = 2OE, DF = 2.