math
posted by lindsay .
Triangle DEF is such that DF=8cm,EF=5.5cm and its area is 11 root2 cm^2. Find angle EFD.

math 
Henry
Area = 0.5*Ef*DF*sinF = 11 cm^2.
0.5*5.5*8*sinF = 11
22*sinF = 11
sinF = 0.5
F = 30o.
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