Tangent to a Circle

Adjust the sliders to change the center and radius of the circle. Move the red point around the circle - what do you notice? Does it matter where the circle is centered or what it's radius is? How can you use this information to find the equation of the tangent line to the circle? To change the viewing window, hold the shift button and left-click to drag the graph or use the scroll wheel to zoom in/out. You can also adjust the axes by holding the shift button and left-click on the axis you want to change.