fix: update math/base/special/cscd to match correct reference implementation

[anandkaranubc]

Resolves none.

Description

What is the purpose of this pull request?

This pull request:

• Fixes the implementation of math/base/special/cscd to align with the correct reference implementation.
• Adds improved test fixtures to enhance accuracy and ensure correctness.

Related Issues

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This pull request:

• resolves none

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• Read, understood, and followed the contributing guidelines.

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@stdlib-js/reviewers

[anandkaranubc]

Reference implementation

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/cscd	$\color{green}186/186$ $\color{green}+100.00\%$	$\color{green}5/5$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}186/186$ $\color{green}+100.00\%$

The above coverage report was generated for the changes in this PR.

[Planeshifter]

LGTM.

[stdlib-bot]

PR Commit Message

fix: update `math/base/special/cscd` to match correct reference implementation

PR-URL: https://github.com/stdlib-js/stdlib/pull/5811

Co-authored-by: Karan Anand <[email protected]>
Reviewed-by: Philipp Burckhardt <[email protected]>

Please review the above commit message and make any necessary adjustments.

[anandkaranubc]

LGTM.

Thanks, @Planeshifter. A quick question: Do you think it is reasonable to return PINF or NINF in these implementations (such as cscd, secd, cotd, and tand) instead of returning null or NaN, which better aligns with the discontinuity of these functions?

[Planeshifter]

@anandkaranubc

I think the current approach of returning +/-Infinity is good because it can propagate through expressions in a predictable way and still return results in numerical applications then; also what Julia opted to do.