Question

Two forces of 30 pounds and 40 pounds act upon a body, forming an acute angle with each other. The angle between the resultant and the 30-pound force is 35degree 10'. Find, to the nearest ten minutes, the angle between the two given forces

Answer 1

angles in the triangle are 
35°10' 
180° - A (with A = angle between the 2 forces) 
A - 35°10' 

40/sin35°10' = 30/sin(A-35°10') 
sin(A-35.17) = 30sin35.17°/40 = 0.432 

A-35.17= 25.6 
A = 60.77° = 60°46' 
60°50'