How do you convert (6, -6) into polar coordinates?

1 Answer
Jan 31, 2016

The point that has coordinates (6, -6)(6,6) in rectangular coordinates has the polar coordinates (sqrt72, -pi/4)(72,π4) or (8.5, -0.79)(8.5,0.79) or (to give a positive value to thetaθ) as (sqrt72, (7pi)/4)(72,7π4).

Explanation:

Polar coordinates are in the form (r,theta)(r,θ) where rr is the distance from the origin (0, 0)(0,0) to the point and thetaθ is the angle in radians from the positive x-axis.

To find the radius, use:

r=sqrt(6^2+(-6)^2) = sqrt(36+36) = sqrt72 = 8.5r=62+(6)2=36+36=72=8.5

(some may prefer to leave it in the form sqrt7272)

To find the value of thetaθ, know that 66 is the opposite and -66 is the adjacent side of a right-angled triangle, so:

tan theta = 6/-6 = -1tanθ=66=1

Therefore theta=tan^-1(-1) = -pi/4θ=tan1(1)=π4 radrad.

This means the polar coordinates can be expressed as (sqrt72, -pi/4)(72,π4) or (8.5, -0.79)(8.5,0.79) or (to give a positive value to thetaθ) as (sqrt72, (7pi)/4)(72,7π4).