Two crewmen pull a boat through a lock. The first pulls with a force of 130 N at an angle of 35 degrees relative to the forward direction of the boat.
The force of 130 N applied by the crewman can be divided into its components, one in the forward direction of the boat that is equal to 130*cos 35 and the other in a perpendicular direction equal to 130*sin 35. If the force applied by the second crewman is F, it can be divided into its components, F*cos 45 in the forward direction of the boat and F*sin 45 in a perpendicular direction.
If the net force of the two should be only in the forward direction, the components F*sin 45 and 130*sin 35 should be equal.
F*sin 45 = 130*sin 35
=> `F = 130*(sin 35/sin 45)`
=> `F ~~ 104.45`
The second crewman should apply a force of 104.45 N.