Reeve.

同樣溫緊mid term的路過

1) F1 represents the force in each of the truss members
∑Fv =  -100 + 2F1cos45 = 0
   F1 = (100√2)/2
   F1 = 70.7 N

2)差唔多
∑Fv  = Fay + Fby - 50 = 0
tan50 = Fax / Fay   .... (1)
tan70 = Fbx / Fby   .... (2)

(1) / (2)
0.43         = 50 - Fay / Fay
1.43 Fay = 50
Fay          = 34.87 N               (As such Fby = 50 - 34.87 = 15.13N)

cos 50 = Fay / Fa
Fa         = 54.25N

cos 70 = Fby / Fb
Fb        = 44.24N

我啲phy還晒比先生, 所以粗粗地睇住先