Videos and lessons to help High School students learn how to prove theorems about lines and angles.

*Theorems include: vertical angles are congruent; when a transversal crosses parallel lines, alternate interior angles are congruent and corresponding angles are congruent; points on a perpendicular bisector of a line segment are exactly those equidistant from the segment’s endpoints*.

Common Core: HSG-CO.C.9

Related Topics:

Common
Core (Geometry)

Common Core
for Mathematics

Proof-Vertical Angles are Equal

Proving that vertical angles are equal.

Corresponding Angles Converse

If two lines are cut by a transversal and the corresponding angles are congruent, then the lines are parallel.

Proof: Alternate Interior Angles Are Congruent

If two parallel lines are cut by a transversal, then the alternate interior angles are congruent.

Proof: Alternate Interior Angles Converse

If two lines are cut by a transversal and the alternate interior angles are congruent, then the lines are parallel.

Proof: Consecutive Interior (Same Side) Angles Are Supplementary

If two parallel lines are cut by a transversal, then the consecutive interior angles are supplementary.

Proof: Consecutive Interior Angles Converse

If two lines are cut by a transversal and the consecutive (same side) interior angles are supplementary, then the lines are parallel.

Proof: Perpendicular Bisector Theorem

If a point is on the perpendicular bisector of a segment, then it is equidistant from the endpoints of the segment.

Proof: Perpendicular Bisector Theorem Converse

If a point is equidistant from the endpoints of a segment, then the point is on the perpendicular bisector of the segment.

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You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

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