已知弦长5.02和弧长5.6求出弓形的面积

已知弦长L=5.02和弧长C=5.6求出弓形的面积S?
弧半径为R,弧所对的圆心角为A.
Rn+1=(1+(L-2*Rn*SIN(C/(2*Rn)))/(L-C*COS(C/(2*Rn))))*Rn
R0=3
R1=3.353
R2=3.482
R3=3.495
R4=3.495
R=3.495
A=C/R=5.6/3.495=1.602289弧度=1.602289*180/PI=91.8度
S=PI*R^2*A/360-(L/2)*R*COS(A/2)
=PI*3.495^2*91.8/360-(5.02/2)*3.495*COS(91.8/2)
=3.681