chore: improve comments and add tests to trapezoidal rule (#11640)

* chore: improve comments and add tests to trapezoidal rule

* fix: too much characters in line

* Update maths/trapezoidal_rule.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Update maths/trapezoidal_rule.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Update maths/trapezoidal_rule.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Update maths/trapezoidal_rule.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* fix: change function name in calls

* modify tests, changes numbers to remove coma

* updating DIRECTORY.md

* Fix doctest whitespace

* Try to fix line length in doctest

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Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>
Co-authored-by: tianyizheng02 <tianyizheng02@users.noreply.github.com>