easy a.maths question~~~

圖片參考：http://i600.photobucket.com/albums/tt87/roastchickens/f44a225e.jpg?t=1236946998

Let VA = 1 ,then AB = 1/tan30 = √3 , AC = 1
By LAW OF COSINE , in △ABC :
BC^2 = (√3)^2 + 1^2 - 2√3(1)cos120
BC^2 = 4 + √3
BC = 2.394170171
BM = CM = BC/2 = 1.197085085
ㄥVMB + ㄥVMC = 180, so cosㄥVMB + cosㄥVMC = 0
cosㄥVMB
= [1.197085085^2 + AM^2 - (√3)^2] / 2(1.197085085)AM
cosㄥVMC = (1.197085085^2 + AM^2 - 1) / 2(1.197085085)AM
so 2(1.197085085^2 + AM^2) - 4 = 0
AM = 0.896055196
Let the angle of elevation of v from n be Z
tan Z = VA / AM = 1 / 0.896055196
Z = 48.138( 3dec.)