This worksheet is a review of circles and lines, and will give you some practice with algebra and with graphing. Also, this worksheet introduces the idea of "tangent lines" to circles. Later on in Math 124, you'll learn how to find tangent lines to many other types of curves. Two circles, called C1 and C2, are graphed below. The center of C_1 is at the origin, and the center of C_2 is the point in the first quadrant where the line y = x intersects C1. Suppose C1 has radius 2. C2 touches the x and y axes each in one point. What are the equations of the two circles?