The reasons that justify the given statements that proves that [tex]\angle 1 \cong \angle 3[/tex] are:
Reason 3: Definition of linear angles.
Reason 4: Definition of supplementary angles
Reason 5: Substitution.
Reason 6: Subtraction property of equality
Reason 7: Definition of congruence
Statement 3:
[tex]\angle 1 $ and $ \angle 2[/tex] are supplementary
[tex]\angle 2 $ and $ 3[/tex] are supplementary
Linear angles on a straight line are supplementary angles. Therefore the reason that justifies statement 3 is: Definition of linear angles.
Statement 4:
[tex]\angle 1 + \angle 2 = 180^{\circ}\\\\\angle 2 + \angle 3 = 180^{\circ}[/tex]
The sum of two angles that are supplementary to each other equals 180 degrees. Therefore the reason for statement 4 is: Definition of supplementary angles
Statement 5:
[tex]\angle 1 + \angle 2 = \angle 2 + \angle 3[/tex]
Since [tex]\angle 1 + \angle 2 = 180[/tex] and [tex]\angle 2 + \angle 3 = 180[/tex],
therefore,
substituting [tex]\angle 2 + \angle 3[/tex] for 180 into [tex]\angle 1 + \angle 2 = 180[/tex] will give us:
[tex]\angle 1 + \angle 2 = \angle 2 + \angle 3[/tex]
We simply substituted here.
Therefore the reason for statement 5 is: Substitution.
Statement 6: [tex]\angle 1 = \angle 3[/tex]
We have, [tex]\angle 1 + \angle 2 = \angle 2 + \angle 3[/tex]
Subtract [tex]\angle 2[/tex]0 from both sides of the equation
[tex]\angle 1 + \angle 2 - \angle 2 = \angle 2 + \angle 3 - \angle 2\\\\\angle 1 = \angle 3[/tex](subtraction property of equality)
Therefore, the reason that justifies statement 6 is: Subtraction property of equality
Statement 7: [tex]\angle 1 \cong \angle 3[/tex]
Definition of congruence states that if two angles are equal in measure, therefore, they are congruent to each other.
The reason that justifies statement 7 is: Definition of congruence
In summary, the reasons that justify the given statements are:
Reason 3: Definition of linear angles.
Reason 4: Definition of supplementary angles
Reason 5: Substitution.
Reason 6: Subtraction property of equality
Reason 7: Definition of congruence
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