R:圆的半径, H:弓形高,L:弦长R �0�5 = (R - H)�0�5 + (L/2)�0�5 H=R-√[R �0�5 -(L/2) �0�5 ]L = 2√[ R �0�5 - (R - H)�0�5 ]
利用垂径定理.即过圆心作玄的垂直线利用勾股定理求出高H,弦长为a,半径为R,H=R-根号下[R^2-(a/2)^2]弦长:l=nπr/180