where "|"A"| = "k"" means the index "A" runs through the set of all subsets of size "k" of the set { 1, 2, 3, ... }. 

In these two identities an asymmetry appears that is not seen in the case of sums of finitely many terms: in each product, there are only finitely many sine factors and cofinitely many cosine factors.

If only finitely many of the terms θ are nonzero, then only finitely many of the terms on the right side will be nonzero because sine factors will vanish, and in each term, all but finitely many of the cosine factors will be unity.

Convenience
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अनन्त पदों के योग की ज्या एवं कोज्या
Pedagogy