(1) In the cube abcd-a1b1c1d1, e and F are the moving points on edges BB1 and CC1 respectively, ab = 1. The volume of the tetrahedron with vertices a, C, B1 and D1 is calculated RT

(1) In the cube abcd-a1b1c1d1, e and F are the moving points on edges BB1 and CC1 respectively, ab = 1. The volume of the tetrahedron with vertices a, C, B1 and D1 is calculated RT

Taking △ ab1c as the bottom and d1b1 as the height (d1b1 vertical plane ab1c), the area of △ ab1c can be obtained by solving the triangle method (because three sides can be obtained)

In the cube abcd-a1b1c1d1 with edge length a, M is the middle point of Aa1. The cross-sectional area obtained by calculating the plane section cube of C, D1, M

From MD1 square = a1d1 square + MA1 square, we get MD1 = √ 5A / 2
From CD1 square = CD square + dd1 square, we get CD1 = √ 2A
From MC square = ma square + AC square, we get MC = 3A / 2
We know that Helen's theorem can be used to find the area of three sides of a triangle
P=(a+b+c)/2
S=√P(P-a)(P-b)(P-c)