depends on what the object is weather its a polygon or just an angle on a graph
but all boils down to the basic 360degrees half of the circle would be a range of 180 degrees, a triangles 3 angles added together =180 degrees. i dont know what type of eaxample you are looking for ill give one with triangles.
if a right triagle has one angle of 60degrees. find the other angles. right triangles are always 90degrees so u have 
if its part of a circle or graph it depends on the wording of the problem
like: line DB is perpindicular to line AC where segment BC and AB are congruent. if line BX is between line AB and DB where angle ABX=13degrees. Find angle XBD.
...since we know the line DB is perpindicular to line AC, there is a 90 degree angle, and we know that angle ABX + angle XBD = 90 degrees, then 13 +
there are alot of ways to find an angle just depends on the values
