User's Manual Part 3

Slope Applications
Use the Slope tool to find the average slope between any two points on the graph.
Longer slope lines tend to produce more accurate slope calculations.
The Slope tool can be used to compare actual data with ideal conditions by
drawing a line with a known slope (to represent the ideal condition) beside a
portion of a Data Plot.
Slope Limitations
Slope calculations are based on logged points connected by the slope line. Points
occur only at the exact time intervals used to record data.
The Slope tool cannot measure slopes when the line is vertical.
This command can be accessed on the Toolbar when the Profile Tab is active.
Slope Button