Answer:
(b) 7.28 cis(105.945°)
Step-by-step explanation:
The trig form of a vector is always ...
magnitude(cos(angle)·i +sin(angle)·j)
Sometimes, that is abbreviated ...
magnitude cis(angle) or magnitude∠angle
where the "angle" is measured counterclockwise from the +x axis.
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The forms showin in choices C and D can be rejected immediately because the sine and cosine coefficients are incorrectly placed. To differentiate between choices A and B, you need to know whether the angle is greater than 90°. The terminal point is above and left of the initial point, so the angle must be more than 90°. (It can help to plot the points on a graph.)
u = 7.28(cos 105.945°i + sin 105.945°j)
