一、新定义一种符号例1记实数x1,x2,…,xn中的最大数为max{x1,x2,…,xn},最小数为min{x1,x2,…,xn}.已知△ABC的三条边的长分别为a,b,c(a≤b≤c),定义它的倾斜度为l=max{a b,b c,c a}·min{a b,b c,c a},则“l=1”是“△ABC为等边三角形”的A.必要而不充分条件B.充分而不必要条件C.充分必要条件 First, the new definition of a symbol example 1 record the real number x1, x2, ..., xn the maximum number of max{x1, x2, ..., xn}, the minimum number of min{x1, x2, ..., xn}. The lengths of the three sides of ABC are known as a, b, c (a ≤ b ≤ c), and its inclination is defined as l=max{ab,bc,ca}·min{ab,bc,ca}. “l=1” is “△ABC is an equilateral triangle” A. necessary but not sufficient condition B. full and unnecessary condition C. sufficient and necessary condition