Double click the trendline equation; from the Number tab select a
format that lets you specify the number of decimal places.

Alternatively, use the LINEST function to get the value in the
worksheet directly. [In versions prior to 2003, for certain data sets,
the chart trendline gave better results than LINEST.]

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Regards,

Tushar Mehta
www.tushar-mehta.com
Excel, PowerPoint, and VBA add-ins, tutorials
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In article ,
says...
Does anyone know how to increase the number of significant digits given for
the slope of a trendline in the trendline equation in Excel?