In the given figure the angles m∠2 and m∠4 can belinked by a Z shaped line, which means they are alternate angles. These types of angles are congruent.
Meaning that m∠2= m∠4
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On the other hand, angles m∠3 and m∠4 are consecutive angles, this means that they add up to 90º
m∠3+m∠4=90º
So, if m∠4 and m∠2 are equal, then if you add m∠3 + m∠2 the resulting angle is also 90º
