Find the points on the curve where the tangent is horizontal or vertical. If you have a graphing device, graph the curve to check your work.x= 3cos(θ)

y= sin(2θ)

The horizontal tangents are

( ± http://www.webassign.net/cgi-bin/sym...2%29%29%2F%202 , ± http://www.webassign.net/cgi-bin/symimage.cgi?expr=1 )

And the vertical tangents are

( http://www.webassign.net/cgi-bin/symimage.cgi?expr=-3 , http://www.webassign.net/cgi-bin/symimage.cgi?expr=0 )

( http://www.webassign.net/cgi-bin/symimage.cgi?expr=3 , http://www.webassign.net/cgi-bin/symimage.cgi?expr=0)

But can someone explain why?