How do you find the polar coordinates given the rectangular coordinates (3,8)?

1 Answer
Nov 18, 2016

Please see the explanation.

Explanation:

The polar coordinate system is an ordered pair (r,theta)(r,θ)

To convert from Cartesian, (x, y)(x,y) to r:

r = sqrt(x^2 + y^2)r=x2+y2

To convert from Cartesian, (x, y)(x,y) to thetaθ:

If x > 0 and y >= 0x>0andy0, then use: theta = tan^-1(y/x)" [1]"θ=tan1(yx) [1]
If x = 0 and y > 0x=0andy>0, then use: theta = pi/2" [2]"θ=π2 [2]
If x = 0 and y < 0x=0andy<0, then use: theta = (3pi)/3" [3]"θ=3π3 [3]
If x < 0x<0, then use: theta = pi + tan^-1(y/x)" [4]"θ=π+tan1(yx) [4]
If x > 0 and y < 0x>0andy<0, then use: theta = 2pi + tan^-1(y/x)" [5]"θ=2π+tan1(yx) [5]

For your point, (3, 8)(3,8):

r = sqrt(3^2 + 8^2) = sqrt(73) " length units"r=32+82=73 length units

Use equation [1]:

theta = tan^-1(8/3)θ=tan1(83)

theta ~~ 1.249 " radians"θ1.249 radians

The polar point is (sqrt(73)" length units", 1.249" radians")(73 length units,1.249 radians)