How do you convert x^2+(y-4)^2=16x2+(y4)2=16 to polar form?

2 Answers
May 3, 2016

r=8sinthetar=8sinθ

Explanation:

If (r,theta)(r,θ) is in polar form and (x,y)(x,y) in Cartesian form the relation between them is as follows:

x=rcosthetax=rcosθ, y=rsinthetay=rsinθ, r^2=x^2+y^2r2=x2+y2 and tantheta=y/xtanθ=yx

Hence, x^2+(y-4)^2=16x2+(y4)2=16 can be written as

x^2+y^2-8y+16=16x2+y28y+16=16 or

x^2+y^2-8y=0x2+y28y=0 or

r^2-8rsintheta=0r28rsinθ=0 or

r(r-8sintheta)=0r(r8sinθ)=0 dividing by rr

r-8sintheta=0r8sinθ=0 or

r=8sinthetar=8sinθ

May 3, 2016

r=8sinthetar=8sinθ

Explanation:

To convert from Cartesian to Polar coordinates use the following formulae that link them.

• x=rcostheta" and " y=rsinthetax=rcosθ and y=rsinθ

x^2+y^2-8y+16=16 " (expanding bracket) "x2+y28y+16=16 (expanding bracket)

rArrr^2cos^2theta+r^2sin^2theta-8rsintheta+16-16=0r2cos2θ+r2sin2θ8rsinθ+1616=0

then r^2(cos^2theta+sin^2theta)-8rsintheta=0r2(cos2θ+sin2θ)8rsinθ=0

using the identity: cos^2theta+sin^2theta=1 cos2θ+sin2θ=1

rArr r^2=8rsintheta" and dividing both sides by r "r2=8rsinθ and dividing both sides by r

rArr r=8sinthetar=8sinθ