Geometry
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Congruent triangles
If you can take one figure and flip, shift and rotate (not resize) it to be identical to another figure, then the two figures are congruent. This topic explores this foundational idea in geometry.
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 Triangles and SSS
- SSS to Show a Radius is Perpendicular to a Chord that it Bisects
- Other Triangle Congruence Postulates
- Two column proof showing segments are perpendicular
- Finding Congruent Triangles
- Congruency postulates
- More on why SSA is not a postulate
- Perpendicular Radius Bisects Chord
- Congruent Triangle Proof Example
- Congruent Triangle Example 2
- Congruent triangles 1
- Congruent triangles 2
Congruence and isosceles and equilateral triangles
This tutorial uses our understanding of congruence postulates to prove some neat properties of isosceles and equilateral triangles.
- Congruent legs and base angles of Isosceles Triangles
- Equilateral Triangle Sides and Angles Congruent
- Equilateral and Isosceles Example Problems
- Triangle types
- Triangle angles 1
- Another Isosceles Example Problem
- Example involving an isosceles triangle and parallel lines
- Figuring out all the angles for congruent triangles example
- Basic Triangle Proofs Module Example
- Basic Triangle Proofs Module Example 2
- Basic triangle proofs
- Fill-in-the-blank triangle proofs example 1
- Fill-in-the-blank triangle proofs example 2
- Fill-in-the-blank triangle proofs
- Wrong statements in proofs example 1
- Wrong statements in triangle proofs
- Problem involving angle derived from square and circle