Question 1065323
Find the rectangular coordinates of the point
whose polar coordinates are: 

{{{(matrix(1,3,-7.2,",",pi/5))}}}
<pre><b>
That's this point:

{{{drawing(400,400,-10,10,-10,10,
graph(400,400,-10,10,-10,10, (.726542528)*x*(sqrt(sin(9x))/sqrt(sin(9x)))*(sqrt(x)/sqrt(x))*(sqrt(4.8-x)/sqrt(4.8-x)) ),
red(arc(0,0,9.2,-9.2,0,36),locate(2,1.9,theta=pi/5),
line(0,0,-7.2cos(pi/5),-7.2sin(pi/5)),

locate(-8,-4.2,(matrix(1,3,-7.2,",",pi/5))),locate(-3.6,-2.7,r=-7.2)),

green(
circle(0,0,1),
circle(0,0,2),
circle(0,0,3),
circle(0,0,4),
circle(0,0,5),
circle(0,0,6),
circle(0,0,7),
circle(0,0,8),
circle(0,0,9),
circle(0,0,10),
circle(0,0,11),
circle(0,0,12),
circle(0,0,13),
circle(0,0,14)) )}}}

Notice in the above graph, that &#952; is in QI, but
r is negative.  So we find the angle {{{pi/5}}}
in QI indicated by the dotted line and the red
arc.  But then since r = -7.2, we go 7.2 units
in the OPPOSITE direction, which puts the point
in QIII.  Now from that point, we draw a perpendicular 
up to the x-axis. 

{{{drawing(400,400,-10,10,-10,10,
graph(400,400,-10,10,-10,10, (.726542528)*x*(sqrt(sin(9x))/sqrt(sin(9x)))*(sqrt(x)/sqrt(x))*(sqrt(4.8-x)/sqrt(4.8-x)) ),
red(arc(0,0,9.2,-9.2,0,36),locate(2,1.9,theta=pi/5),
line(0,0,-7.2cos(pi/5),-7.2sin(pi/5)),

locate(-8,-4.2,(matrix(1,3,-7.2,",",pi/5))),locate(-3.6,-2.7,r=-7.2),
line(-7.2cos(pi/5),0,-7.2cos(pi/5),-7.2sin(pi/5))


),

green(
circle(0,0,1),
circle(0,0,2),
circle(0,0,3),
circle(0,0,4),
circle(0,0,5),
circle(0,0,6),
circle(0,0,7),
circle(0,0,8),
circle(0,0,9),
circle(0,0,10),
circle(0,0,11),
circle(0,0,12),
circle(0,0,13),
circle(0,0,14)) )}}}

So the x-ccordinate of the point is 

{{{x = r*cos(theta)=-7*cos(pi/5) = -5.824922359}}}

and the y-coordinate of the point is

{{{x = r*sin(theta)=-7*sin(pi/5) = -4.232053817}}}

The point in rectangular coordinates to three significant
digits is (-5.82,-4.23)

Edwin</pre>