The Third Angles Theorem is based on the Triangle Angle Sum Theorem. Is there a similar theorem for quadrilaterals?
Is the sum of the measures of the interior angles of a quadrilateral always constant?
Practice makes perfect
Let's remember what the Third Angles Theorem states.
If two angles of one triangles are congruent
to two angles of a second triangle,
then the third angles of the triangles
are congruent.
This theorem is based on the fact that the sum of measures of the interior angles of any triangle equals 180^(∘), which is the Triangle Angle Sum Theorem.
To know if the same strategy works when working with quadrilaterals, a question we could ask ourselves is Is the sum of the measures of the interior angles of a quadrilateral always constant?
To answer the question above, use the fact that a quadrilateral can be divided into two triangles.
