3 sentences

1. 勾股定理是几何学中一个非常著名的定理。

   gōu gǔ dìng​lǐ shì jǐ​hé​xué zhōng yī gè fēi​cháng zhù​míng de dìng​lǐ.

   The Pythagorean theorem is a very famous theorem in geometry.

   Source: Dong Chinese Dictionary

2. 勾股定理中的“弦”指的就是直角三角形的斜边。

   gōu gǔ dìng​lǐ zhōng de“ xián” zhǐ de jiù shì zhí​jiǎo sān​jiǎo​xíng de xié biān.

   The 'xian' in the Pythagorean theorem refers to the hypotenuse of a right triangle.

   Source: Dong Chinese Dictionary

3. 我们可以从这个数学定理中得出几个重要的推论。

   wǒ​men kě​yǐ cóng zhè​ge shù​xué dìng​lǐ zhōng dé​chū jǐ gè zhòng​yào de tuī​lùn.

   We can derive several important corollaries from this mathematical theorem.

   Source: Dong Chinese Dictionary