【思维导图】【名师箴言】人说几何很困难,难点就在辅助线;辅助线,如何添?把握定理和概念.计算半径与弦长,弦心距来中间站;是直径,成半圆,想成直角径连弦.圆上若有一切线,切点圆心半径连;切线长度要计算,勾股定理最方便.要想作个外接圆,各边作出中垂线;还要作个内接圆,内角平分线梦圆. 【Mind Map】 【Master Proverbs】 People say that geometry is very difficult, difficult in the auxiliary line; auxiliary line, how to add to grasp the theorem and concepts. Calculate radius and chord length, chord center to the middle station; is diameter, into a semicircle , Want to be at right angles to the string .If there is a circle on the circle, the tangent radius of the circle center; tangent length to be calculated, the Pythagorean theorem is most convenient .To make a circumscribed circle, the sides make a vertical line; Inscribed circle, the angle bisector dream circle.