# Thread: Precal help.. word problem w/ vectors

1. ## Precal help.. word problem w/ vectors

okay here's the problem:
The magnitude and direction of two forces acting on an object are 70 pounds, S56°E, and 50 pounds, N72°E, respectively. Find the magnitude, to the nearest hundreth of a pound, and the direction angle, to the nearest tenth of a degree, of the resultant force.

how do i find the magnitude and the direction angle?

everytime i sketch out the graph, it turns out weird. i do not understand this at all and when i do get an answer, it is incredibly different than the answer in the back.

2. Originally Posted by needmathhelptoujours
okay here's the problem:
The magnitude and direction of two forces acting on an object are 70 pounds, S56°E, and 50 pounds, N72°E, respectively. Find the magnitude, to the nearest hundreth of a pound, and the direction angle, to the nearest tenth of a degree, of the resultant force.

how do i find the magnitude and the direction angle?

everytime i sketch out the graph, it turns out weird. i do not understand this at all and when i do get an answer, it is incredibly different than the answer in the back.

directions relative to the + x-axis (east)

$R_x = 50\cos(18) + 70\cos(-34)$

$R_y = 50\sin(18) + 70\sin(-34)$

magnitude, $|R| = \sqrt{R_x^2 + R_y^2}$

direction, $\theta = \arctan\left(\frac{R_y}{R_x}\right)$