This is a common proof strategy in math. If you want to show two values a and b are equal, proving (1) a cannot be greater than b and (2) a cannot be less than

This is a common proof strategy in math. If you want to show two values a and b are equal, proving (1) a cannot be greater than b and (2) a cannot be less than b is often easier by proving (1) and (2) separately rather than directly proving they are equal.