What is the polar form of <mstyle displaystyle="true"> ( - 4 ,

Reginald Hanna

Reginald Hanna

Answered question

2022-06-03

What is the polar form of ( - 4 , 32 ) ?

Answer & Explanation

ran1suel23

ran1suel23

Beginner2022-06-04Added 3 answers

Step 1
The rectangular point ( - 4 , 32 ) is in the form ( x , y )
Polar points are in the form ( r , θ ) .
To find r, we effectively need to find the hypotenuse of the right triangle with legs of x and y.
Thus, r = x 2 + y 2 . Here, this becomes
r = ( - 4 ) 2 + ( 32 ) 2 = 4 2 + 32 2 = 4 2 + 4 2 ( 8 2 ) = 4 2 ( 1 + 8 2 ) = 4 65
Even though the point ( - 4 , 32 ) is in Quadrant II, the value of r is a magnitude and is still positive.
To find θ , we first need to write some statement involving θ given the information that we know.
Looking at the image, we have θ , the side opposite θ , and the side adjacent to θ in a right triangle. Thus, we can say
tan θ = opposite adjacent = y x
Solving for θ :
θ = tan - 1 ( y x )
Using our known values:
θ = tan - 1 ( 32 - 4 ) = tan - 1 ( - 8 ) = - 1.44644133
Note, however, that this is a negative value and that - 1.44644133 > - π 2 , so this is really an angle in Quadrant IV.
To find the value of this angle in Quadrant II, we know that it will be π minus the magnitude of the angle we determined.
That is,
θ = π - 1.44644133 = 1.69515132
So, our point is:
( r , θ ) = ( 4 65 , 1.69515132 )

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