This tool checks a selection set of geometry for proper tangency between arcs and adjacent segments (be they straight or also arcs). It flags points where the non-tangency occurs with red marker inserts. You can then move about the drawing making corrections as needed.
Keyboard Command: InqTanChk
It works on a selection set of LINE, ARC, LWPOLYLINE or POLYLINE objects. All selected geometry is internally broken down into the primitives of line and arc for comparison (your geometry is unchanged). That means that the end of a polyline can be compared to an arc or line that shares the common point.
There are tolerance values that allow you to loosen up the standard if desired, the defaults are 0.0001 for angular and 0.0000001 for distance.