23.17
5^2+(x-2.5)^2=x^2
25+x^2-5x+6.25=x^2
31.25=5x
x=6.25
l=6.25*2π*2*arcsin（5/6.25）/360
=25πarccos0.8/360
=25π53.13/360
=23.17
已知圆弧的弦长10m和弧高2.5m,求弧长
23.17
5^2+(x-2.5)^2=x^2
25+x^2-5x+6.25=x^2
31.25=5x
x=6.25
l=6.25*2π*2*arcsin（5/6.25）/360
=25πarccos0.8/360
=25π53.13/360
=23.17