Question

Prove: Quadrilateral ABCD is a parallelogram.

Answer 1

Answer:

Step 3.

m∠ AEB = m∠ CED .........By  Vertical Angles Theorem.

Step-by-step explanation:

Vertical Angles Theorem:

Vertical angle theorem states that vertical angles, angles that are opposite each other and formed by two intersecting lines,are congruent.

If two lines intersect each other we have two pair of vertical opposite angles. As shown in the figure.

Here,

∠ 1 and ∠ 2 are vertical opposite angles and also they are equal.

∠ 3 and ∠ 4 are also vertical opposite angles and also they are equal.

For,

step 3. m∠ AEB = m∠ CED

Therefore, the reason for step 3 of this proof is Vertical Angles Theorem.