Sometimes I am not able to completely see math objects.A screen shot have been added. I was using a different font. I also tried using the default font i.e. Liberation Serif but the issue was not resolved.
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and
image 3.png
I also thought that the issue will be resolved if I export a PDF document but it was same.
Image 1.png
I have libreoffice 6.4.4.2
The answer you are looking for was peripheral to a question asked earlier. ajlittoz wrote an answer that I remembered because I had noticed the problem on occasion myself. The question 232542/letter-alpha-in-math was about clarity of a font but the answer at the bottom of the page answers your question.
" In Math, Format>Spacing and select Category Borders There you can give some “breathing” to your formula: I set Toip and Bottom to 0.10 which reveals more of the top shape. Experiment to find the optimal improvement."
Thanks to @EarnestAl to link to my previous answer (which I couldn’t find again). I took the liberty to edit slightly the link for better clarity.
