calculus
posted by sarah .
three forces with magnitudes 100, 50, and 80 lb act on an object at angles of 50 degree, 160 degree, and 20 degree respectively. ind the direction and magnitude o the resultant force.

express each as a vector in component form
magnitude 100,direction 50
= (100cos50, 100sin50) = (64.279 , 76.604)
mag50,direction160
= (8.682 , 17.101
mag80, direction 20
= ( 75.175 , 27.361)
add up the 3 vectors
= (130.772 , 66.344)
magnitude = √(x^2 + y^2) = 146.638
direction :
tan Ø = 66.344/130.772
Ø = 26.9° or 333.1°
but my sketch showed the resultant to be in the first quadrant, so
Ø = 26.9° 
mag50,direction160 = (46.985,17.101)

you messed up mag50, direction160
=(46.984, 17.101