老轨
幼苗
共回答了11个问题采纳率:81.8% 举报
设圆方程为y=√(R²-x²),(加不加负号一样的啊)
那么
y'= -x /√(R²-x²),(y')²=x²/(R²-x²)
y"= [-√(R²-x²) - x²/√(R²-x²)] / (R²-x²)
= -R²/(R²-x²)^(3/2)
而
曲率半径R'
=(1+y'²)^(3/2)/ |y"|
=[1+ x²/(R²-x²)]^(3/2) / [ R²/(R²-x²)^(3/2)]
=[ R²/(R²-x²)]^(3/2) / [ R²/(R²-x²)^(3/2)]
= R^3 /R²
=R
所以推出来曲率半径就是圆的半径
1年前
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