How to expand trimmed body text to full body text in the same Views page?
Consider using the Views Accordion module. Here is an excerpt from its project page:


  ... provides a display style plugin for the Views module.
  It will take the results and display them as a JQuery accordion, using the first field as the header for the accordion rows.
  
  For Drupal 7 the module integrates the jQuery UI Accordion plugin as a views style plugin. You can configure the options provided by the jQuery UI plugin.