Throughout the ages, progressivelly more accurate values have been found for pi. By the 1850's, it was calculated to 707 decimal places. By the 1950's, a computer calculated pi to 100,000 places. It is the base of natural logarithms. As n becomes infinitely large, e approximates 2.71828 in value.
Formulas using ex appear in applications ranging from statistics to nuclear physics.
Yes, i would be a number, which when multiplied by itself, would equal negative one. It can immediately be replaced with a division by 100. May have to convert from metric to conventional units or visa versa. From giving intraveneous medications to taking pulses, health care workers use math to convert from grains to milligrams, pounds to kilograms, and others. Calculate distance, time, fuel requirements, corrections from true magnetic north, etc.