Abstract
We evaluate some new explicit values of quotients of Ramanujan’s theta functions and use them to find explicit values of Ramanujan’s continued fractions.
1. Introduction
Ramanujan’s general theta function is defined by Two important special cases of are the theta functions and [1, page 36, Entry 22] defined by, for , where
In his notebooks [2], Ramanujan recorded many explicit values of theta functions and . All these values were proved by Berndt [3, page 325] and Berndt and Chan [4]. Yi [5] introduced the parameter for positive real numbers and defined by and used the particular case to find explicit values . Baruah and Saikia [6] defined the parameter for positive real numbers and as and used the particular case to find explicit values . Saikia [7] also established some explicit values .
In this paper, we consider the particular cases and of the parameters and , respectively. By using theta function identities, we find some new explicit values of the parameters and . Particularly, we evaluate and for 3/2, 2/3, 6, 1/6, 5/2, 2/5, 10, and 1/10. Previously, Yi [5] evaluated for 1, 3, 1/3, 9, 1/9, 5, 1/5, 25, and 1/25. Saikia [8] evaluated for 2, 1/2, 4, 1/4, 7, 1/7, 49, and 1/49. Baruah and Saikia [6] evaluated for 1, 3, 1/3, 9, 1/9, 5, 1/5, 25, 1/25, 7, 1/7, 13, 1/13, 49, and 1/49. As an application to our new values, we evaluate some old and new explicit values of Ramanujan’s cubic continued fraction and a continued fraction of order twelve which are, respectively, defined by, for , The continued fraction was recorded by Ramanujan on page 366 of lost notebook [9]. We refer to [10–14] for explicit evaluations of . The continued fraction was introduced by Naika et al. [15]. We refer to [8, 15] for explicit evaluations of .
The presentation of the paper is as follows. In Section 2 we record some preliminary results for ready references in this paper. Section 3 is devoted to explicit evaluations of the parameters and . In Section 4 we use new explicit values of and to evaluate some explicit values of the continued fractions and .
We end this introduction by noting the following remarks regarding and from [6, page 1764, Theorem 4.1] and [5, page 385, Remark 2.3], respectively.
Remark 1. The parameter has positive real value with and increases as increases.
Remark 2. The parameter has positive real value with and the values of decrease as increases.
2. Preliminary Results
Lemma 3 (see [16, Theorem 3.2]). If and , then
Lemma 4 (see [16, Theorem 3.1]). If and , then
Lemma 5 (see [16, Theorem 3.2]). If and , then
Lemma 6 (see [16, Theorem 3.9]). If and , then
Lemma 7 (see [5, page 385, Theorem 2.2]). For all positive real numbers and , one has
Lemma 8 (see [6, page 1764, Theorem 4.1]). For all positive real numbers and , one has
Lemma 9 (see [5, page 393, Theorem 4.9(i)]). For any positive real number , one has
Lemma 10 (see [5, page 394, Theorem 4.12(i)]). For any positive real number , one has
Lemma 11 (see [6, page 1769, Theorem 5.1(i) and (iii)]). For any positive real number , one has(i), (ii) + = + .
3. Explicit Evaluations of the Parameters and
In this section, we prove some general theorems for the explicit evaluations of the parameters and and evaluate some new explicit values therefrom.
Theorem 12. One has
Proof. We set in Lemma 3 and use the definition of .
Corollary 13. One has
Proof. Setting in Theorem 12 and simplifying using Lemma 8, we obtain Solving (16) for and noting the fact in Remark 1, we find that Again, setting in Lemma 11(i) and simplifying using Lemma 8, we deduce that Eliminating from (18) using (17) and simplifying, we obtain Solving (19) and noting the fact in Remark 1, we obtain Employing (20) in (17) and simplifying, we obtain Now the values of and follow from the values of and , respectively, and Lemma 8.
Theorem 14. One has
Proof. We set in Lemma 4 and use the definitions of and .
Corollary 15. One has
Proof. Setting in Theorem 14 and simplifying using Lemma 7, we obtain Employing (17) in (24), solving the resulting equation, and noting the fact in Remark 2, we deduce that Again setting in Lemma 9 and simplifying using Lemma 7, we obtain Employing (25) in (26), solving the resulting equation, and noting the fact in Remark 2, we deduce that Multiplying (25) and (27), we evaluate the value of , and dividing (25) by (27) and simplifying, we evaluate the value of . Now the values of and easily follow from the values of and , respectively, and Lemma 7.
Theorem 16. One has
Proof. We set in Lemma 5 and use the definition of .
Corollary 17. One has where
Proof. Setting in Theorem 16 and simplifying using Lemma 8, we obtain
Solving (31) and noting the fact in Remark 2, we find that
Again, setting in Lemma 11 (ii) and simplifying using Lemma 8, we obtain
Employing (32) in (33), solving the resulting equation, and noting the fact in Remark 1, we obtain
where , , and .
Combining (32) and (34), we calculate the values of and . Then, the values of and follow from the values of and , respectively, and Lemma 8.
Theorem 18. One has
Proof. We set in Lemma 6 and use the definitions of and .
Corollary 19. One has where is given in Corollary 17, , and + .
Proof. Setting in Theorem 18 and simplifying using Lemma 7, we get
Employing (32) and solving the resulting equation, we obtain
Again setting in Lemma 10 and simplifying using Lemma 7, we find that
Employing (38) in (39), solving the resulting equation, and noting the fact in Remark 2, we obtain
where is given in Corollary 17, , and + + .
Combining (38) and (40), we evaluate the values of and . Then the values of and follow from and , respectively, and Lemma 7.
4. Explicit Evaluations of Continued Fractions
This section is devoted to finding some explicit values of the continued fractions and by using new values of and evaluated in Section 3.
Lemma 20 (see [6, page 1788, Theorem 9.1(i)]). One has
Theorem 21. One has where , , and are given in Corollary 17.
Proof. We set 3/2, 6, 2/3, 1/6, 5/2, 10, 2/5, and 1/10 in Lemma 20 and use the corresponding values of from Corollaries 13 and 17 to complete the proof.
The explicit values of , , , , and are new.
Lemma 22 (see [8, page 144, Theorem 5.1]). One has
By setting 3/2, 6, 2/3, 1/6, 5/2, 10, 2/5, and 1/10 in Lemma 22 and employing the corresponding values of from Corollaries 15 and 19, we calculate the following new explicit values of the continued fraction .
Theorem 23. One has where is given in Corollary 17 and and are given in Corollary 19.
Conflict of Interests
The author declares that there is no conflict of interests regarding the publication of this paper.
Acknowledgment
The author is thankful to the University Grants Commission, New Delhi, India, for partially supporting the research work under Grant F. no. 41-1394/2012(SR).