π = 3.14159 26535 89793 23846 …
= 4 ∫_{0}^{1} \sqrt{1 − x^{2}} dx
= \frac{22}{7} − ∫_{0}^{1} \frac{x^{4}(1 − x)^{4}}{1 + x^{2}} dx
= −\sqrt{−1} log (−1)
= RootOf[sin x]  (3 < x < 4)
= 4 (∫_{0}^{∞} e^{−x^{2}}dx)^{2}
= 4 arctan 1
= 16 arctan \frac{1}{5} − 4 arctan \frac{1}{239}

= \sqrt{6 ∑_{n=1}^{∞} \frac{1}{n^{2}}}

= \sqrt{\frac{6}{∏_{primes p}1 − \frac{1}{p^{2}}}}

= 3 + \frac{1}{7 + \frac{1}{15 + \frac{1}{1 + \frac{1}{292 + ⋯}}}}

= 3 + \frac{1^{2}}{6 + \frac{3^{2}}{6 + \frac{5^{2}}{6 + \frac{7^{2}}{6 + \frac{9^{2}}{6 + ⋯}}}}}

= \frac{9801}{\sqrt{8} ∑_{n=0}^{∞} \frac{(4n)!(1103 + 26390n)}{(n!)^{4}396^{4n}}}