[ 物理 ]急問phy 問題(mechanic)

http://i.4cdn.org/sci/1414989953859.jpg

圖中問題
A block of mass is suspended from the ceiling by a string. Two forces F1 and F2 cause the string to bend as shown in the figure. The section AB of the string makes an angle of α=44.9 degree with the horizontal line. The mass of the block is m=77.8kg. What is the tension of section AB of the string? Refer to the figure in the file "figures for assignment " g=9.8ms-2 The answer should be in unit of N.

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