Find VM if the dihedral angle formed by the intersection of ABCD and triangle VB

/in /by

Find VM if the dihedral angle formed by the intersection of ABCD and triangle VB

Given:  Square ABCD and each side is 16

             Equilateral triangle is VBC

  M is the midpoint of AD

What is the length of VM if the dihedral angle formed by the intersection of triangle VBC and ABCD is 30 degrees?

is 90 degrees? is 0 degrees?  is n degrees?20150321_174209.jpg 20150321_173900.jpg 20150321_173825.jpg 

Ignore everything that is handwritten in the table