在单位圆中,圆心角的弧度数与它所对弧的弧度数相等,圆心角的三角函数值可以用三角函数线来表示。利用单位圆的上述特点.证明某些既含角又含三角函数的三角不等式,往往可以使证明过程既简练又 In the unit circle, the number of arcs of the central angle is equal to the number of arcs it has for the arc, and the trigonometric function of the central angle can be represented by a trigonometric function line. Using the above characteristics of the unit circle, we prove that some triangular inequalities that contain both angles and trigonometric functions can often make the proof process concise.