神马作文网已知弦长12.5m,9m,求弧长.急.
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已知弦长12.5m,9m,求弧长.急.
已知弦长L=12.5m,弓高H=2.9m,求弧长C?
弧的半径为R,弧所对的圆心角为A.
R^2=(R-H)^2+(L/2)^2
R^2=R^2-2*R*H+H^2+L^2/4
2*R*H=H^2+L^2/4
R=H/2+L^2/(8*H)
=2.9/2+12.5^2/(8*2.9)
=8.185m
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((12.5/2)/8.185)
=99.565度
=99.565*PI/180
=1.73774弧度
C=A*R
=1.73774*8.185
=14.223m
弧的半径为R,弧所对的圆心角为A.
R^2=(R-H)^2+(L/2)^2
R^2=R^2-2*R*H+H^2+L^2/4
2*R*H=H^2+L^2/4
R=H/2+L^2/(8*H)
=2.9/2+12.5^2/(8*2.9)
=8.185m
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((12.5/2)/8.185)
=99.565度
=99.565*PI/180
=1.73774弧度
C=A*R
=1.73774*8.185
=14.223m