In △ ABC, ∠ C = 90 °, AC = 2.1cm, BC = 2.8cm. (1) find the area of △ ABC; (2) find the length of hypotenuse AB; (3) find the length of height CD

In △ ABC, ∠ C = 90 °, AC = 2.1cm, BC = 2.8cm. (1) find the area of △ ABC; (2) find the length of hypotenuse AB; (3) find the length of height CD

As shown in the figure: (1) s △ ABC = 12ac × BC = 2.94; (2) AB = ac2 + BC2 = 3.5; (3) 12bc × AC = 12ab × CD, the solution is: CD = 1.68

As shown in the figure, in △ ABC, ab = AC = 41cm, D is the point on AC, DC = 1cm, BD = 9cm

∵ AC = 41cm, DC = 1cm, ∵ ad = 40cm, ∵ 402 + 92 = 412, ∵ abd is a right triangle, the area of ∵ ABC is 12 · AC · BD = 12 × 41 × 9 = 184.5 (cm2)

As shown in the figure, D, e and F are the middle points of the triangle ABC
 

Triangle ABC, triangle ace and triangle BCF are equilateral triangles whose sides are AB, AC and BC of triangle ABC respectively. It is proved that ADFE is a parallelogram

I don't know if you have drawn the graph wrong. The graph is like this. These triangles are on the same side of BC, that is to say, point D is actually on the same side of D and E. but you can't draw the three regular triangles up and down in this way. The following is the proof. You really don't give many points. I hope you can add a little