Two lines are perpendicular if they intersect at a right angle. If two lines form a right angle, or congruent adjacent angles, then the lines are perpendicular. If the exterior sides of two adjacent acute angles are perpendicular, then the angles are complementary.

1. 2­5 Perpendicular Lines
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2. 2

3. Perpendicular Lines
Two lines that intersect to form right angles.
We can conclude that:
If two lines are perpendicular then
each angle is a right angle.
If one of the angles is a right angle then
the lines are perpendicular
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4. Theorems that go along with perpendicular lines:
If two lines are perpendicular,
then they form congruent adjacent angles
If two lines form congruent adjacent angles,
then the lines are perpendicular.
If the exterior sides of two adjacent acute angles
are perpendicular,
then the angles are complimentary
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5. SPICSA
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2 ­ 16 even
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6. 6