This is the first time I've tried to use Trendlines in charts in this fashion and it's not working for me. I chart a two column cell range with resistance on the x-axis and temperature on the y-axis. I draw either a 4th order poly or log trendline. I want to test the equation so I display the trendline equation on the chart and then copy it into a cell. When I enter a value for the x-axis resistance the resulting temperature I get from the equation is nowhere near the trendline on the chart. What am I doing wrong here?