Question

(Q7) Determine the graph of the polar equation r = 12/6+4 cos theta.

Answer 1

ANSWER

b.

EXPLANATION

The given polar equation is,

$r = \frac{12}{6 + 4 \cos( \theta) }$

Cross multiply to get,

$r(6 + 4 \cos( \theta) ) = 12$

$6r + 4r\cos( \theta) ) = 12$

Substitute,

$r\cos( \theta) = x$

and

$r = \sqrt{ {x}^{2} + {y}^{2} }$

$6 \sqrt{ {x}^{2} + {y}^{2} } + 4x = 12$

$3\sqrt{ {x}^{2} + {y}^{2} } + 2x = 6$

$3\sqrt{ {x}^{2} + {y}^{2} } = 4 - 2x$

$9({x}^{2} + {y}^{2}) =( 4 - 2x ) ^{2}$

$9{x}^{2} + 9 {y}^{2} =16 - 16x + 4x ^{2}$

$5{x}^{2} + 9 {y}^{2} + 16x = 16$

This is an ellipse whose center is shifted to the left with orientation on the x-axis

The correct choice is B.