I know how to pronounce the first symbol as "theta", but the other symbol that looks like a circle with a vertical slash, I don't know what to call it.
I would appreciate any help. Thank you
That's lowercase Greek phi, pronounced with an initial f sound and rhyming with English pie, lie or sky. That said, some speakers may pronounce it rhyming with English see, key or me.
See https://en.m.wikipedia.org/wiki/Phi for more details.
Please check the entire Greek alphabet, as you can find it in this Wikipedia page: https://en.wikipedia.org/wiki/Greek_alphabet.
I must add that there are two ways to write the letter $phi$ in MathJax (or LaTeX):
For such a query, you might find it quicker to use one of the following tools:
Google Image Reverse Search: Navigate to google.com and upload an image of the symbol. Google will display similar images and web pages that feature these images. By examining these, you can find the name of the symbol.
Detexify: Visit Detexify and draw the symbol. The website will provide you with the LaTeX command for the symbol, which usually corresponds to its name.
Chat Bots: ChatGPT can definitely recognize symbols. Other alternatives include Claude and Gemini by Google.