和圆有关的角主要研究圆心角，圆周角，弦切角，圆内接四边形的内角、外角及其他一般角的性质和应用。在以圆为框架的习题中，证明三角形全等、相似，成比例线段，两线段相等等问题，往往都涉及到这些角，其中圆周角是核心，弧起桥梁作用。下面分角的计算与证明，进行一般方法 The angles related to the circle mainly study the properties and applications of the central angle, the circumferential angle, the chord angle, the inner corner, the outer corner, and other general corners of the circle inscribed quadrilateral. In the exercises that use the circle as the frame, the proof that triangles are equal, similar, proportional line segments, two line segments, etc., often involve these angles, in which the circle angle is the core and the arc serves as a bridge. Calculate and prove the following sub-angles, perform general methods