Answer:
m∠1 + m∠3 = m∠2 + m∠4 CANNOT be proven.
Explanation:
When two straight lines intersect one another, four angles are formed. The angles directly opposite each other are called vertical angles and are always congruent. Congruent angles mean they each have the same angle measure.
This means that in this figure, ∠1 is congruent to ∠3 and ∠2 is congruent to ∠4. Using this knowledge, we can prove answer choices 1 and 3.
When two adjacent angles (angles next to each other) form a straight angle, we know they add up to 180° degrees. Two angles that add to 180° are known as supplementary angles. Using this knowledge, we can prove answer choice 2.
Answer choice 4 is the only statement left that cannot be proven by the figure.