Super big problem of ninth grade mathematics ... to be answered by experts ... urgent ~ ~ ~ What I want is the problem-solving process! ! ! This is the 20 10 Qingdao mid-term exam. )
Because point B and point D coincide, we can get BF=DF, so BF+FC=DF+FC=5CM, then AB=DC=3CM. Because the triangle DCF is a right triangle, the square of FC+the square of DC = the square of DF, and then we can set the equation according to the previous formula. Let DF=x, FC=y, then X+Y. Y= 1.6, x=3.4, triangle area = 1.6*3/2=2.4, then the triangle AED and DFC areas are equal, then the total rectangular area =2 triangular DFC+2 triangular DEF areas.