3 sentences

1. 这个数学公式的取值范围是多少？

   zhè​ge shù​xué gōng​shì de qǔ zhí fàn​wéi shì duō​shao?

   What is the range of values for this mathematical formula?

   Source: Dong Chinese Dictionary

2. 老师在黑板上写下了一个数学公式。

   lǎo​shī zài hēi​bǎn shàng xiě​xià le yī gè shù​xué gōng​shì.

   The teacher wrote a mathematical formula on the blackboard.

   Source: Dong Chinese Dictionary

3. 在数学公式中，我们常用希腊字母套来表示常数。

   zài shù​xué gōng​shì zhōng, wǒ​men cháng​yòng Xī​là zì​mǔ tào lái biǎo​shì cháng​shù.

   In mathematical formulas, we often use the Greek letter tau to represent constants.

   Source: Dong Chinese Dictionary