When a rectangular coordinate system is established with the fixed point of a parabola as the origin and the symmetry axis of the parabola as y, the relation of the parabola can be set as

When a rectangular coordinate system is established with the fixed point of a parabola as the origin and the symmetry axis of the parabola as y, the relation of the parabola can be set as

When a rectangular coordinate system is established with the vertex of the parabola as the origin and the symmetry axis of the parabola as y, the relation of the parabola can be set as
y=ax²

There is a parabola shaped viewing arch bridge ABC in a park. Its cross section is shown in the figure. In the rectangular coordinate system established in the figure, the analytical expression of parabola is y
There is a parabola shaped viewing arch bridge ABC in a park. Its cross section is shown in the figure. In the rectangular coordinate system established in the figure, the analytical expression of parabola is y=-
one
twenty
X2 + C and passing vertex C (0,5) (length unit: m)
(1) Write the value of C directly;
(2) Now, due to the celebration activities, it is planned to lay a carpet with a width of 1.5m along the surface of the steps of the arch bridge. The price of the carpet is 20 yuan / m2. How much does it cost to buy the carpet?
(3) In the reinforcement and maintenance of arch bridge, the "scaffold" is rectangular efgh (H and G are on the left and right sides of parabola respectively), and the inclined plane eg is laid. It is known that the perimeter of rectangular efgh is 27.5m, and the inclination angle of inclined plane eg ∠ GEF is calculated (accurate to 0.1 °)

(1) because vertex C (0,5), C = 5, so OC = 5, let y = 0, that is - 120x25 = 0, the solution is X1 = 10, X2 = - 10, ∧ AB = 10 - (- 10) = 20, ∧ the total length of carpet is: ab 2oC = 20, 2 × 5 = 30, ∧ 30 × 1.5 × 20 = 900 (yuan)