Given :
\Force F1 magnitude = 47 N
\Force F1 inclined angle θ1 = 18º ( with positive X-axis in counter clockwise direction )
\Force F2 magnitude = 74 N
\Force F2 inclined angle θ2 = 280º ( with positive X-axis in counter clockwise direction )
\θ2 = 360 - 280 = 80º ( with positive X-axis in clockwise direction )
\Resultant Force magnitude F =?
\Resultant Force angle θ = ?
\From above figure
\Force F1 magnitude OA = BC = 47 N
\Force F2 magnitude OB = AC = 74 N
\Resultant Force magnitude F = OC
\Force F1 in X-Axis direction F1x = OA cos18
\F1x = 47 cos18
\F1x = 44.7
\Force F1 in Y-Axis direction F1y = OA sin18
\F1y = 47 sin18
\F1y = 14.52
\Force F2 in X-Axis direction F2x = OB cos(80)
\F2x = 74 cos(80)
\F2x = 12.8
\Force F2 in Y-Axis direction F2y = OB sin(80)
\F2y = 74 sin80
\F2y = 72.88
\F2y direction is downwards.So
\F2y = - 72.88
\Sum of all forces in X-Axis direction ΣFx = F1x+F2x
\ΣFx = 44.7+12.8
\ΣFx = 57.5
\Sum of all forces in Y-Axis direction ΣFy = F1y+F2y
\ΣFy = 14.52-72.88
\ΣFy = -58.36
\F = √ [( ΣFx )2+ ( ΣFy )2]
\F = √ [ 57.52 + (-58.36)2 ]
\F = √ [6712.1396]
\F = 81.93 N
\Resultant Force magnitude is 81.93 N
\Θ = tan-1( ΣFy / ΣFx )
\Θ = tan-1(-58.36/57.5)
\Θ = - 45.43o
\Negative symbol indicates clockwise direction (downwards) with positive X-axis.
\Resultant Force angle is 45.43º with positive X-axis in clockwise direction
\