Eight thin steel plates are 2.4m long and 1m wide, weighing 6kg. Cut a disc with d = 80cm from the top. How much does the disc weigh? It's a thin steel plate. It's wrong. It's not eight I need a process

Eight thin steel plates are 2.4m long and 1m wide, weighing 6kg. Cut a disc with d = 80cm from the top. How much does the disc weigh? It's a thin steel plate. It's wrong. It's not eight I need a process

3.14 * 0.4 * 0.4 △ 2.4 * 6 = 1.256 kg

As shown in the figure, △ ABC is an equilateral triangle, point D is a point on the edge BC, with AD as the edge to make equilateral △ ade, passing through point C to make CF parallel de intersection AB and point F, if point D is BC
The middle point on the edge is proved to be EF = CD

Let AB = BC = AC = 2, ed intersect AB at point G ∵ △ ABC is an equilateral triangle, D is the midpoint of BC, ad is the height of ABC, and ∵ △ ade is an equilateral triangle

As shown in the figure, in RT △ ABC, ∠ ACB = 90 °, ab = 10, BC = 8, point d moves on BC (does not move to B, c), de ‖ AC, intersects AB with E, let BD = x, the area of △ ade is y. (1) find the functional relationship between Y and X and the value range of independent variable x; (2) when x is the value, the area of △ ade is the largest? What is the maximum area?

(1) In RT △ ABC, AC = AB2 − BC2 = 102 − 82 = 6, ∵ tanb = 68 = 34. ∵ de ∥ AC, ∵ BDE = ∠ BCA = 90 °. ∵ de = BD · tanb = 34x, CD = bc-bd = 8-x. let the height of de edge in △ ade be h, ∵ de ∥ AC, ∵ H = CD. ∵ y = 12de · CD = 12 × 34x · (8-x), that is y = − 3