This is an example of a typical semi-geometric model. Please look for knowledge about geometric models on the Internet by yourself.

The proof of this problem is as follows: connecting BD, S triangular bed =S triangular AEB (according to equal base height), S triangular BDF=S triangular BCF (according to equal base height), S square ABCD=S triangular ABE+S triangular bed +S triangular BDF+S triangular BCF=2*(S triangular BDE+S triangular BDF). To sum up, double S triangular BDF.

Hope to adopt