If you borrow words, phrases, images, audio, video or ideas, then yes, you ALWAYS need to cite your sources—and that is in any class, not just technical writing. Otherwise, you are plagiarizing.
- For your major projects, use the style that is appropriate for your career field. For instance, electrical engineers use IEEE, and biologists often use CSE.
- For homework, you can use the format that makes sense. For a borrowed image, for instance, you can include a credit line in the image caption or at the end of the document. As long as I can tell what you borrowed and where it came from, you’re fine.