# Category:Triangles

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This category contains results about **Triangles** in the context of **Geometry**.

Definitions specific to this category can be found in **Definitions/Triangles**.

## Subcategories

This category has the following 68 subcategories, out of 68 total.

### A

- Angle Bisector Theorem (2 P)

### B

- Brocard Points (1 P)

### C

- Ceva's Theorem (3 P)

### E

- Euler Line (1 P)
- Euler Triangle Formula (9 P)
- Exradii of Triangles (empty)

### F

- Fermat Problem (3 P)
- Fermat-Torricelli Point (empty)
- Feuerbach Circles (3 P)
- Fleenor-Heronian Triangles (1 P)
- Fontené Theorems (9 P)

### H

### I

- Isogonal Conjugates (empty)

### L

- Law of Cosines (12 P)
- Law of Sines (9 P)
- Law of Tangents (7 P)
- Length of Angle Bisector (4 P)

### M

- Medial Triangles (4 P)
- Menelaus's Theorem (3 P)
- Midline Theorem (4 P)
- Morley's Trisector Theorem (4 P)

### N

- Napoleon's Theorem (6 P)
- Nine Point Circle Theorem (4 P)

### O

- Oblique Triangles (empty)

### P

- Parallel Transversal Theorem (3 P)
- Principal Parts of Triangle (empty)

### R

### S

- Scalene Triangles (2 P)
- Secondary Parts of Triangle (empty)
- Sign of Area of Triangle (empty)
- Solution of Triangle (empty)
- Steiner Inellipse (empty)
- Steiner-Lehmus Theorem (8 P)

### T

### W

- Wallace-Simson Line (1 P)

## Pages in category "Triangles"

The following 102 pages are in this category, out of 102 total.

### A

### C

- Ceva's Theorem
- Circumscribing about Circle Triangle Equiangular with Given
- Circumscribing Circle about Triangle
- Congruence of Triangles is Equivalence Relation
- Construction of Parallelogram equal to Triangle in Given Angle
- Construction of Parallelogram on Given Line equal to Triangle in Given Angle
- Construction of Triangle from Given Lengths
- Converse Hinge Theorem
- Cosine of Half Angle in Triangle
- Crossbar Theorem

### E

- Equal Sized Triangles on Equal Base have Same Height
- Equal Sized Triangles on Same Base have Same Height
- Equiangular Triangles are Similar
- Equiangular Triangles are Similar/Proof 2
- Euler Triangle Formula
- Every Triangle has 2 Equal Sides
- External Angle of Triangle equals Sum of other Internal Angles
- External Angle of Triangle is Greater than Internal Opposite

### G

### L

- Largest Parallelogram Contained in Triangle
- Largest Rectangle Contained in Triangle
- Lateral Face of Prismatoid is Triangle, Trapezium or Parallelogram
- Law of Cosines
- Law of Sines
- Law of Tangents
- Length of Angle Bisector
- Length of Angle Bisector in terms of Angle
- Length of Circumradius of Triangle
- Length of Inradius of Triangle
- Length of Side of Triangle as Cosines of Angles
- Line Parallel to Side of Triangle which Bisects One Side also Bisects Other Side
- Lines Through Endpoints of One Side of Triangle to Point Inside Triangle is Less than Sum of Other Sides
- Lines Through Endpoints of One Side of Triangle to Point Inside Triangle is Less than Sum of Other Sides/Corollary

### M

### N

### P

### R

### S

- Sides of Equiangular Triangles are Reciprocally Proportional
- Similar Figures on Sides of Right-Angled Triangle
- Similar Polygons are composed of Similar Triangles/Porism
- Simson Line Theorem
- Sine of Angle of Triangle by Semiperimeter
- Sine of Half Angle in Triangle
- Sine of Twice Angle minus Sum of Sines of Twice Other Two Angles of Triangle
- Square equals Sum of Squares implies Right Triangle
- Steiner-Lehmus Theorem
- Stewart's Theorem
- Sum of Angles of Triangle equals Two Right Angles
- Sum of Cosines of Angles in Triangle
- Sum of Cosines of Four Times Angles of Triangle
- Sum of Cosines of Twice 2 Angles minus Cosine of Twice Third Angle of Triangle
- Sum of Cosines of Twice Angles of Triangle
- Sum of Cotangents of Half Angles in Triangle
- Sum of Sides of Triangle in terms of Circumradius and Half Angle Cosines
- Sum of Sines of Angles in Triangle
- Sum of Sines of Twice Angles of Triangle
- Sum of Tangents of Angles in Triangle
- Sum of Two Sides of Triangle Greater than Third Side

### T

- Tangent of Half Angle in Triangle
- Triangle Angle-Angle-Side Congruence
- Triangle Angle-Side-Angle and Side-Angle-Angle Congruence
- Triangle Angle-Side-Angle and Side-Angle-Angle Congruence/Proof
- Triangle Angle-Side-Angle Congruence
- Triangle Congruence
- Triangle Side-Angle-Angle Congruence
- Triangle Side-Angle-Side Congruence
- Triangle Side-Side-Side Congruence
- Triangles with One Equal Angle and Two Other Sides Proportional are Similar
- Triangles with Proportional Sides are Similar
- Triangles with Two Sides Parallel and Equal
- Two Angles of Triangle are Less than Two Right Angles
- Two Ears Theorem