一、三角函数的基本概念涉及本考点知识的高考命题热点:(1)判断角所在的象限;(2)求角的取值范围;(3)三角函数值的大小比较;(4)三角函数求值.例1已知下列四个命题:①若点P(a,2a)(a≠0)为角α终边上的一点,则sinα=2“5;5②若α,β都是第一象限角,且αβ,则tanαtanβ;③若θ是? First, the basic concept of trigonometric functions involves the hot spots of the college entrance examination proposition: (1) Judging the quadrant in which the corner is located; (2) The range of values ​​for the angle; (3) Comparison of the values ​​of the trigonometric function; (4) Trigonometric functions Evaluation. Example 1 is known as the following four propositions: 1 If the point P(a, 2a)(a≠0) is a point on the end of the angle α, then sinα=2”5; 52 if α, β are The first quadrant angle, and αβ, then tanαtanβ; 3 if θ is?