Question

:)

Answer 1

Your angle is 30.594°

http://www.triangle-calculator.com/?what=sss&a=13.3&b=10.8&c=6.8&submit=Solve

I suggest use law of cosines to calculate angle in SSS triangle

Answer 2

law of cosines: 6.8^2 = 13.3^2 + 10.8^2 - 2*13.3*10.8*cos x

x = arccos((6.8^2 -13.3^2 - 10.8^2)/(-2*13.3*10.8)) = 30.597°

Answer 3

cos x = 0.86079 so angle is x =30.597°

Answer 4

yes :) Result I manually calculated I checked with online triangle calculator:

http://www.triangle-calculator.com/?what=sss&a=13.3&b=10.8&c=6.8&submit=Solve

Answer 5

EcoBoost - Your solution is OK , but round errors take same minor numerical difference.

Answer 6

I see - DEF is triangle and unknown angle is EFD :)

EFD = arccos((13.3^2 -6.8^2 - 10.8^2)/(-2*6.8*10.8)) = 95.473°