When writing expressions for complex numbers, what does i represent?

The physical fitness of an athlete is often measured by how much oxygen the athlete takes in (which is recorded in milliliters per kilogram, ml/kg). the mean maximum oxygen uptake for elite athletes has been found to be 60 with a standard deviation of 7.2. assume that the distribution is approximately normal.

The number of fish in a lake can be modeled by the exponential regression equation y=14.08 x 2.08^x where x represents the year

Ab based on the given diagram, if m_1 = 60° then m 2 = 30 60 90 180