If the edge length of cubic abcd-aibicidi is 2 and M is the midpoint of DDI, the volume of triangular pyramid bi-amc is?
Because Ab1 = B1C, and the triangle line ab1c is an equilateral triangle, take the midpoint n of AC to connect b1n, so b1n is perpendicular to AC
And am = MC, triangle AMC is isosceles triangle line, connecting Mn, Mn is perpendicular to AC
So we can calculate the volume immediately
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