SOLUTION: What type of directrix does this conic have? r = 4/-2-cosθ or https://s10.postimg.org/kbq3bkdpl/r_-2_-cos.png A.) Vertical B.) Horizontal C.) Oblique D.) No directrix.

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Question 1080588: What type of directrix does this conic have? r = 4/-2-cosθ or https://s10.postimg.org/kbq3bkdpl/r_-2_-cos.png
A.) Vertical
B.) Horizontal
C.) Oblique
D.) No directrix.
Found 2 solutions by MathLover1, ikleyn:
Answer by MathLover1(20850)   (Show Source): You can put this solution on YOUR website!


.....compare to and you see that:
and and



Since , we have the equation of an ellipse. The form of the equation tells us that the directrix is perpendicular to the polar axis and that its Cartesian equation is which is vertical line.
so, answer is: A.)

Answer by ikleyn(52879)   (Show Source): You can put this solution on YOUR website!
.
Dear tutor MathLover1 !


Do you agree that the radius "r" in polar coordinates is always positive and can not be negative ?


If you do agree, then how the formula r =  can produce the positive r ?


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