Question 631548
<pre>
r = 4·sin{{{theta}}}

That is a circle of diameter 4. Since it is sine the very bottom of the
circle is at the pole (origin).  If it were cosine the pole (origin)
would be at the far left side of the circle.

That one is easy to change to rectangular form

Replace sin@ by {{{y/r}}}

r = 4({{{y/r}}})

Multiply both sides by r

r² = 4y

Change r² to x² + y²

x² + y² = 4y

x² + y² - 4y = 0

Complete the square by adding 4 to both sides:

x² + y² - 4y + 4 = 4

x² + (y - 2)² = 4

Write x as (x - 0)

(x - 0)² + (y - 2)² = 2²

which is a circle with center (0,2) with radius 2.

Edwin</pre>