Question

线段AB,BD在平面a内,BD垂直AB,线段AC垂直平面a,且AB=a,BD=b,AC=c,求CD间的距离

Answer 1

CD^2=AC^2+AD^2=AC^2+BD^2-AB^2=c^2+b^2-a^2

CD=√(c^2+b^2-a^2)