Refer to the diagram shown below.

Vector a is 2.8 cm long and 60° above the x-axis in the first quadrant. Therefore it s represented by

Vector b is 1.9 cm long and 60° below the x-axis in the fourth quadrant. Therefore it is represented by

The vectors may be written as

a = 2.8*(cos60°, sin60°) = (1.445, 2.5028)

b = 1.9*(cos60°, -sin60°) = (0.950, -1.6454)

Part (a)

a + b = (1.445+0.950, 2.5028-1.6454)

= (2.395, 0.8574)

The magnitude of this vector is

√[2.395² + 0.8574² ] = 2.5438 cm

Its direction is

tan⁻¹ (0.8574/2.395) = 19.7° above the x-axis, in the first quadrant.

The resultant vector is shown in the figure below.

Part (b)

Similarly obtain

a - b = (0.495, 4.1485)

The magnitude is 4.1777.

The direction is 83° above the x-axis, in the 1st quadrant.

The resultant vector is shown in the figure below.

Part (c)

Similarly, obtain

b - a = (-0.495, -4.1483)

The magnitude is 4.1777.

The direction is 83° below the negative x-axis, in the 3rd quadrant.

The resultant vector is shown in the figure below.