The left side of the equation is equal to
OA? -What? +OB? -An overdose? +OC? -OE?
The right side of the equation is equal to
OB? -What? +OC? -An overdose? +OA? -OE?
The two formulas are equal, so the conclusion holds.
⑵ Using the conclusion of the previous question, all the formulas on the right side of the equation are moved and obtained by the square difference formula.
(AF+FB)(AF-FB)+(BD+DC)(BD-DC)+(CE+EA)(CE-EA)= 0
Because af+FB = BD+DC = ce+ea > 0 (because the equilateral tangents of three sides of a regular triangle are greater than 0
So there is
AF-FB+BD-DC+CE-EA=0
Finishing can get the required formula.