Magnitude and angle counterclockwise from the + x direction

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SUMMARY

The discussion focuses on calculating the magnitude and angle of a vector expressed as -25.3i - 1.2j. The correct angle is determined using the arctan function, with adjustments based on the signs of the vector components. Specifically, since both components are negative, 180 degrees is added to the arctan result of 2.72, yielding a final angle of 182.72 degrees. This method ensures accurate representation of the vector's direction in the Cartesian plane.

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  • Knowledge of trigonometric functions, particularly arctan
  • Familiarity with angle measurement in degrees
  • Basic skills in vector magnitude calculation
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Homework Statement


Express your answer in part (a) in terms of magnitude and angle counterclockwise from the + x direction.
Vector = -25.3i-1.2j


Homework Equations


arctan(ady/adx)


The Attempt at a Solution


Arctan(-1.2/25.3)=2.72
This is wrong... but I have no idea how to fix it.
 
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Since tan is a trig function that repeats every 90deg, some consideration must be put into the signs of x and y. Since x and y are both negative, 180deg must be added to the value calculated to obtain the correct value. Likewise, if y is negative and x is positive, 270deg must be added. If x is negative and y is positive, 90deg must be added. This is shown when looking at a plot of the tan function. To confirm this answer (182.72), plug it into tan and see if it gives you your y/x ratio.
 


Thank you very much that worked.
 

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