Cartesian coordinates are represented as the ordered pair, #(x, y)#, and can be converted to polar coordinates, represented as #(r, theta)#, using the following three identities.

#x=rcos(theta)#

#y=rsin(theta)#

#r=sqrt(x^2 + y^2)#

Lets start by finding #r#. Plugging #x# and #y# into the identity for #r# yields;

#r = sqrt(5^2 + 0^2) = sqrt(5^2) = 5#

If we plug #x# and #r# into the first identity, we get;

#5 = 5cos(theta)#

#5/5 = cos(theta)#

#1= cos(theta)#

On the unit circle, #cos(0) = 1#, so #theta = 0#. Our ordered pair is therefore;

#(r, theta) = (5, 0)#