Question

Show that the relation y^2 = 10x - x^2 can be expressed in polar coordinates as r = 10 cos theta. Help please!

Answer 1

sigh...just think about it

y = rsin(angle)
x = rcos(angle)

y^2+ x^2 = r^2 * (cos(angle)^2 + sin(angle)^2) = 10 * r cos(angle)
=> r^2 = 10 r cos angle
=> r = 10 cos angle

Answer 2

Add the x^2 over.
x^2+y^2=10x.
Well x^2+y^2=r^2 and x=rcos(theta)
So just plug in:
r^2=10rcos(theta)
r=10cos(theta)

Answer 3

r^2 = x^2+y^2
x = r cos(t)

x^2 +y^2 = 10x ; change to indentities

r^2 = 10r cos(t) ; /r

r = 10 cos(t)