Tangent - Running Object Snap

Draw a line from the endpoint of the arc
Snap to the tangent of the circle

Draw line start from the tangent of the circle
Snap to the tangent of an arc

Draw a curcle
Snap to the tangent of the line

Draw a circle
Snap to the tangent of an arc

You can draw:
Line tangent to circle
Line tangent to arc
Circle tangle to line
Circle tangent to arc