
Gladys S. answered 12/05/20
ASVAB, Algebra, Geometry, and PreCalculus Tutor
) ( -1,-3) lies in Quadrant III. We obtain the r-component of the polar form using
r = √(x2 † y2) = √((-1)2 † (-3)2 ) =√ 10
Using the tan-1 ( calculator) function you will obtain a value for θ in degrees in range (-π /2, π/2) .
However, to obtain θ over the range (0, 2π) it must be adjusted ( in addition to converted to radians).
The rule is
For θ in the range [π/2,π) add π to the calculator value
For θ in the range [π, 3π/2) add π to the calculator value
For θ in the range [3π/2, 2π) add 2π to the calculator value
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θ = tan-1 (-3/-1) = 1.249 radians = 71.56 degrees
You will need to adjust the value of θ in Quadrant III (as shown below) to get in in range
so θ = 1.249 radians + π radians ~ 1.249 radians +3.14 radians = 4.43 radians ~ 253.8 degrees
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so your final answer is r = √ 10 and θ = 4.43 radians which describes a point in polar coordinates in Quadrant III.