If EF = de + BF, then ∠ ECF = (). How do you get it, please give a brief introduction There is a little E on the edge ad of square ABCD, and a little f on ab. if EF = de + BF, then ∠ ECF = (). How do you get it, please give a brief explanation Don't be fussy when explaining, try to use mathematical laws and symbols (I'm junior one, please use the rotation change of junior one to solve this problem)

If EF = de + BF, then ∠ ECF = (). How do you get it, please give a brief introduction There is a little E on the edge ad of square ABCD, and a little f on ab. if EF = de + BF, then ∠ ECF = (). How do you get it, please give a brief explanation Don't be fussy when explaining, try to use mathematical laws and symbols (I'm junior one, please use the rotation change of junior one to solve this problem)

What does EF = de + BF mean? The triangle CDE and the triangle BCF are folded inward to get the triangle CEF, which is the meaning of the equation. In this way, the angle DCE + angle BCF = angle ECF, and the sum of these three angles is a right angle, so it is not difficult to find ∠ ECF = 45 degrees