Steps to Reproduce: 1. Make a new chart with some data. 2. Enter edit mode on the chart by double-clicking it. 3. Create a new trend line by clicking on Insert > Trend Lines... 4. In the resulting dialog, check the checkbox for "Show Equation". 5. Click "Ok" to close the dialog. 6. Double-click on the equation you just inserted. Expected Result: The equation is editable, just like a text box (which it closely resembles). Actual Result: The equation is not editable.
*** This bug has been marked as a duplicate of bug 77744 ***