Khan Academy on a Stick : Congruent triangles

Khan Academy on a Stick

Geometry

Points, lines, and planes
Angles and intersecting lines
Congruent triangles
Perimeter, area and volume
Similarity
Right triangles
Special properties and parts of triangles
Quadrilaterals
Circles
Logical reasoning
Transformations
Worked Examples

Congruent Triangles and SSS
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What it means for triangles to be congruent
SSS to Show a Radius is Perpendicular to a Chord that it Bisects
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More on the difference between a theorem and axiom. Proving a cool result using SSS
Other Triangle Congruence Postulates
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SSS, SAS, ASA and AAS postulates for congruent triangles. Showing AAA is only good for similarity and SSA is good for neither
Two column proof showing segments are perpendicular
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Using triangle congruency postulates to show that two intersecting segments are perpendicular
Finding Congruent Triangles
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Using the SSS, ASA, SAS, and AAS postulates to find congruent triangles
More on why SSA is not a postulate
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SSA special cases including RSH
Perpendicular Radius Bisects Chord
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Simple proof using RSH postulate to show that a radius perpendicular to a chord bisects it
Congruent Triangle Proof Example
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Proving that a point is the midpoint via triangle congruency
Congruent Triangle Example 2
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Showing that segments have the same length

Congruence postulates

We begin to seriously channel Euclid in this tutorial to really, really (no, really) prove things--in particular, that triangles are congruents. You'll appreciate (and love) what rigorous proofs are. It will sharpen your mind and make you a better friend, relative and citizen (and make you more popular in general). Don't have too much fun.

Congruent legs and base angles of Isosceles Triangles
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Showing that congruent legs imply equal base angles and vice versa
Equilateral Triangle Sides and Angles Congruent
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Showing that all of the angles of an equilateral triangle are 60 degrees
Equilateral and Isosceles Example Problems
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Three example problems involving isosceles and equilateral triangles. 2 from Art of Problem Solving (by Richard Ruscyk) book
Another Isosceles Example Problem
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Possible angles for an isosceles triangle
Example involving an isosceles triangle and parallel lines
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Integrating what we know about isosceles triangles and parallel lines
Figuring out all the angles for congruent triangles example
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Another example of using congruency to figure out a bunch of angles
Problem involving angle derived from square and circle
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Challenging problem to find an angle

Congruence and isosceles and equilateral triangles

This tutorial uses our understanding of congruence postulates to prove some neat properties of isosceles and equilateral triangles.