Let's consider the triangle whose interior angles are ∠ 2, ∠ 3, and ∠ 4.
On the figure, the red marker indicates that the two lines are perpendicular. This means that ∠ 4 is a right angle.
m∠ 4=90
According to Corollary 4.2 to the Triangle Angle-Sum Theorem, the other two angles, ∠ 2 and ∠ 3, must be acute. Therefore, out of these three angles, ∠ 4 has the greatest measure.
