13: THANKS HWHELPER

17: Point by point, a dilation transforms the circle x^2 - 6x + y^2 - 8y = -24 onto the circle x^2 - 14x + y^2 - 4y = -44. Find the center and the magnification factor of this transformation.

Also:

19: Use the unit circle to find sin 240 and cos 240? -- (How do I use a unit circle to tell that?! I don't need an answer, I just need someone to point me in the right direction =/ I know what a unit circle is, I just have no idea how I can use that to find sin 240 and cos 240. I know that if I graph (cos theta, sin theta) I get a unit circle. Do I somehow use that to help me?)

20: Given that cos 80 = .0173648, explain how to find cos100, cos 260, cos 280, and sin 190 without using a calculator.