函数的定义域是使问题有意义和表达式(如果函数由解析式给出)在实数范围内有意义的自变量取值集合的交集。本文举例说明定义域的求法。例1.在半径为1的半圆内有一内接等腰梯形ABCD,AB为半圆直径(如图),试求等腰梯形周长和腰长的函数关系,并求出 The domain of the function is the intersection of the set of meaningful values ​​that make the problem meaningful and the expression (if the function is given by the analytic) within the range of real numbers. This article illustrates the method of defining a domain. Example 1. There is an inscribed isosceles trapezoid ABCD in a semicircle with a radius of 1, AB is the semicircle diameter (as shown in the figure), try to find the relationship between the circumference of isosceles trapezoid and the length of the waist, and find