In mathematical reasoning, a statement that results immediately from a proposition that has already been demonstrated as a clear consequence.
A corollary is a simple proposition that results from the proposition demonstrated by reasoning.
Example
Here is a proposition:
The measure in degrees of an inscribed angle is equal to half of the measure in degrees of the arc intercepted on the circle by its sides.
If m\(\stackrel{\frown}{\textrm{AB}}\) = 84,
then m\(∠{\textrm{ABC}}\) = 42.
A corollary resulting from this proposition would be:
Every inscribed angle in a half-circle is a right angle.
m\(∠{\textrm{ABC}}\) = 90.