$x=\cos t+\cos 2t$ and $y = \sin t+\sin 2t$ at $(-1,1)$
I did dy/dt and dx/dt and then dy/dx and got $\displaystyle \frac{\cos t+2\cos 2t}{-\sin t-2\sin 2t}$
Now I'm confused, do I plug in the -1 and 1 to get two answers and then subtract them from each other to the get a final slope? I need to get the slope so that I can make an equation in the y=mx+b form.