Unit 1.4.7, of BUS101:Introduction to business, says "Business cycles are usually measured by considering the growth rate of real gross domestic product."
It also defines an expansion as the time when GDP rises and a contraction as the time when GDP declines.
At the end of the lesson is the following graph:
For some reason, they give a graph of GNP rather than GDP but following the definitions, since the y axis is showing the "growth rate," does this mean that the first point where the line crosses the x axis is a trough because the rate goes from negative (that is decreasing GDP/GNP) to positive (i.e. increasing GDP/GNP)?