I don't know much about it myself Take it as a reference. You'd better buy a foreign textbook.
Prove: Prove
Because ..., ......
Therefore, therefore. . . We can know. . . .
That is to say,
"Because, so" can be replaced by mathematical symbols.
When (x=? ) , ......(y=? ) When (x=? ),(y=? )
Let one side of the rectangle be GE=FH=X and the area of the rectangle be