What are the polar coordinates of (18, −6)?

1 Answer
Jim G.
Jan 23, 2016

( 6sqrt10 , - 0.32 )

Explanation:

Using the formulae that links Cartesian to Polar coordinates .

• r^2 = x^2 + y^2

• theta = tan^-1 (y/x )

[ The point (18 , -6 ) is in the 4th quadrant and care must be

taken to ensure theta is in the 4th quadrant. ]

(here x = 18 and y = - 6 )

r^2 = 18^2 + (-6)^2 = 324 + 36 = 360

rArr r = sqrt360 = 6sqrt10

and theta =tan^-1 (-6/10) = - 0.32 color(black)(" radians ")

This is an angle in the 4th quadrant.

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