How do you find the missing angle in a circle?

-- Collect all of the information you're given ... such as the dimensions of the

circle or of additional lines drawn inside the circle or touching it, and the size

of other angles that are not missing.

-- Recall and collect the various laws, relations, and formulas you know that

relate to circles, or to whatever other shapes have been added to the drawing

you have of the circle with the missing angle.

-- Identify one or two of the mathematical or geometric operations you know

that can make the connection between the given information and the missing

angle.