Applied Mechanics and Graphic Statics
The necessary condition of equilibrium of a body is:

Algebraic sum of vertical components of all the forces must be zero
All (A), (B) and (C)
Algebraic sum of horizontal components of all the forces must be zero
Algebraic sum of the moments of the forces about a point must be zero

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Applied Mechanics and Graphic Statics
The resolved part of the resultant of two forces inclined at an angle θ in a given direction is

Arithmetical sum of the resolved parts of the forces in the direction
Sum of the forces multiplied by the tangent θ°
Algebraic sum of the resolved parts of the forces in the direction
Difference of the forces multiplied by cosine θ°

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