Help with geometry! :)

Hi, can anyone help me with this please, it's really urgent!

1) Convert the following circles, given in parametric form, to Cartesian (x-y) form.

(a) x= -Cos(Theta) , y= -Sin(Theta)
(b) x= 1+Cos(Theta) , y= 1-Sin(Theta)
(c) x= 2+aCos(Theta) , y= 1-aSin(Theta)
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And these two questions please!

(a) - Which two points with x coordinates x=2 lie on the circle (x-1)^2+y^2=16?

(b) Give the equations of the tangents to the circle at these two points.