The standard form is this: "because" is represented by ∵, "so" is represented by ∴ (don't confuse), then write the process, and then write the reason after the process, and the reason is enclosed by ().

For example, as shown in figure ∠ 1 = ∠ 2, try to prove that AB=CD.

∫≈ 1 =∠2 (known)

∴AB=CD (same angle, two straight lines are parallel)

If the teacher doesn't clearly stipulate that it should be so standardized, you can express it directly with words and figures (expressions) without writing like this, and the meaning is very clear.

For example, the question just now can be answered as follows: since ∠ 1=∠2 is known, we can know that AB=CD from the fact that congruence angles are equal and two straight lines are parallel. It is best to have a neat format and clear organization.

You just learned Chapter 7, didn't you? If you want to say that my proof question is ok, you can ask me any questions. ?

PS: Give me the best one for typing so many words. =)

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