# What does this notation (unmatched right parenthesis after a summation) mean?

My textbook contains this notation:

$$\sum_{n=0}^{\infty} r^{2n}\cos n\theta \bigg) ^2 + \quad \sum_{n=0}^{\infty} r^{2n} \sin n\theta \bigg) ^2$$

What does this notation mean? Square the result of the summation? Square each term of the summation?

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What textbook are you using? –  Clayton Feb 5 '13 at 3:23
@Clayton: The textbook is "Mathematical Methods in the Physical Sciences" by Mary L. Boas, Third Edition. I'm looking for errata now. –  Matthew Feb 5 '13 at 3:27
@Clayton: See my comment on DoctorBatmanGod's answer--it was a typographical error. –  Matthew Feb 5 '13 at 3:29
Glad it was cleared up! –  Clayton Feb 5 '13 at 3:31

## 1 Answer

I have a strong feeling this is a typographical error. This would make sense with the added parentheses. Have you googled the name of your textbook and errata? That usually turns up some sort of online list, at least for reasonably new books.

The only time I can think of where unmatched parentheses are used is in defining half open intervals, e.g. $$(a,b] \text{ or } [a,b)$$

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You nailed it: math.tamu.edu/~boas/Boas_MathematicalMethods_errata.pdf See page 79, problem 12. –  Matthew Feb 5 '13 at 3:28
@Matthew Awesome! Glad I could help. –  Sam DeHority Feb 5 '13 at 3:29