Generally speaking, HowNet duplicate checking system will check the contents of formulas, but not all formulas will be repeated. When the formula appears in the form of text, the duplicate checking system of HowNet will calculate the repetition rate of the formula part according to the standard that 13 characters will be judged as duplicates. However, when the formula appears in the form of a picture, the HowNet duplicate checking system will not check the picture part of the formula.

In addition, if the formula editor such as Mathtype is used to insert, HowNet will recognize the formula as a picture when checking the duplicate, so that it will not check the duplicate and will not affect the duplicate checking rate of the paper.

Therefore, it is suggested that students should not use a lot of formula content, so as to avoid the situation that the repetition rate of papers will increase when HowNet checks the duplicate.

HowNet and VIP are systems used by most schools, and their databases are authoritative. Paperfree and papertime are auxiliary revision references, which provide free weight checking, machine weight reduction, online revision and other functions, covering about 70% of HowNet's data, which can reduce the absolute cost of pre-test fees. To be on the safe side, it is recommended to use the duplicate checking system required by the school or institution for testing.