Determine whether the forces are pulling at right angles to each other. explain. 3.5 lb, 6.2 lb, resultant force 9.1 lb
a. yes; 3.52 + 6.22 = 9.12
b. no; a + b > c
c. no; 3.52 + 6.22 ≠ 9.12
d. yes; a + b > c

The resultant force in this item, is that which connects the heads of the magnitude of the given vectors. The magnitude of the resultant force can be calculated through the Pythagorean theorem which states that the square of the resultant force should be equal to the sum of the squares of the smaller forces. That is,
          A² + B² = C²

Investigating the vector values, 
 A² + B² = (3.5 lb)² + (6.2 lb)² = 50.69 lb²
C² = (9.1 lb)² = 82.81 lb²

Since the Pythagorean theorem is not satisfied by the given set of forces then, the forces are not in right angle. 

The answer to the question is letter C.