已知
弦长b=11.2m;弓形高h=2.2m;求弓形的面积S。
解:园半径R=(b²+4h²)/(8h)=(11.2²+4×2.2²)/(8×2.2)
=(125.44+19.36)/17.6=144.8/17.6=8.23m
园心角θ=4arctan(2h/b)=4arctan(4.4/11.2)=4arctan0.3929
=4×21.4477°=85.7908°=85.7908×π/180=1.4973(rad)
故弓形的面积S=(1/2)R²(θ-sinθ)=(1/2)8.23²(1.4973-sin85.7908°)
=33.8665(1.4973-0.9973)=16.9333m²