q餘弦函數是餘弦函數的q模擬
c o s q ( x ) = ∑ n = 0 ∞ ( 1 − q ) 2 n ( − 1 ) n ∗ x 2 n ( q ; q ) 2 n {\displaystyle cos_{q}(x)=\sum _{n=0}^{\infty }{\frac {(1-q)^{2n}(-1)^{n}*x^{2n}}{(q;q)_{2n}}}}
其中的符號 : ( q ; q ) 2 n {\displaystyle :(q;q)_{2n}} 是Q階乘冪
Frank Oliver,NIST Handbook of Mathematical Functions, p422, Cambridge University Press, 2010