E is the base of natural logarithm. Simply put, e is the value of a that makes the slope of an image with y = a 1 at x=0. Approximate E =: 2.7182818284 59045 23536 02874 71352 66249 77572 47093 6995 95749 66967 62772 40766 30353 As for the derivative of E, we + 1/2! + 1/3! +...+ 1/n！ =∑ 1/n！ "it is defined as: when n->; When ∞, the limit is (1+1/n) N. Note: x y stands for the y power of x, you see, with the increase of n, the base is closer to1,and the exponent tends to infinity. Does the result tend to be 1 or infinite? Actually, it tends to be 2.7 1828 ... If you don't believe me, please use a calculator to calculate, and take n = 1, 10, 100 respectively. However, because the general calculator can only display about 10 digits, no matter how many digits, it can't be seen. E is widely used in science and technology, and the logarithm with the base of 10 is generally not used. After studying advanced mathematics, you will know that many formulas can be simplified with E as the base, which is the most "natural" to use, so it is called "natural logarithm".