Sign up ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

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?

share|cite|improve this question
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 Pirocchi Feb 5 '13 at 3:27
@Clayton: See my comment on DoctorBatmanGod's answer--it was a typographical error. – Matthew Pirocchi Feb 5 '13 at 3:29
Glad it was cleared up! – Clayton Feb 5 '13 at 3:31

1 Answer 1

up vote 4 down vote accepted

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. $$(a,b] \text{ or } [a,b)$$

share|cite|improve this answer
You nailed it: See page 79, problem 12. – Matthew Pirocchi Feb 5 '13 at 3:28
@Matthew Awesome! Glad I could help. – Sam DeHority Feb 5 '13 at 3:29

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.