$ 100- 25cos (20) = 76.5076 $
Force in member ob.
We divide the tributory of 75 N by this to get the cos(b-a) 75/ 76.5076 = 0.98029
Arccos (0.98029)= 11.3934
This added to 20 is angle beta.
Beta = 20 + 11.3934 = 31.3934
And Omega = 180- 31.3934= 148.606
Sum of angle in a triangle =180° Omega=180-(70+31.394)
