diff --git a/client/src/pages/guide/english/mathematics/3-by-3-determinants/index.md b/client/src/pages/guide/english/mathematics/3-by-3-determinants/index.md
index 4538cf38a63..75f22f847e6 100644
--- a/client/src/pages/guide/english/mathematics/3-by-3-determinants/index.md
+++ b/client/src/pages/guide/english/mathematics/3-by-3-determinants/index.md
@@ -2,7 +2,7 @@
title: 3 by 3 Determinants
---
## 3 by 3 Determinants
-
+### Method 1
Consider the following matrix, which we will call A:
@@ -57,6 +57,171 @@ For example, consider the following matrix, which we will call B:
det(B) = (-41) - 100 - 90 = -231
+### Method 2
+This method it similar to 2 by 2 determinants, and based on opertations with diagonals
+Again, consider the following matrix, which we will call A:
+
+
+
+ a |
+ b |
+ c |
+
+
+ d |
+ e |
+ f |
+
+
+ g |
+ h |
+ i |
+
+
+
+Then the determinant of this matrix, denoted det(A), is given by:
+
+det(A) = a * e * i + b * f * g + c * d * h - c * e * g - f * h * a - i * b * d
+
+Note how three top-right to bottom-left diagonals are positive
+
+
+
+ a |
+ |
+ |
+
+
+ |
+ e |
+ |
+
+
+ |
+ |
+ i |
+
+
+
+
+
+ |
+ b |
+ |
+
+
+ |
+ |
+ f |
+
+
+ g |
+ |
+ |
+
+
+
+
+
+ |
+ |
+ c |
+
+
+ d |
+ |
+ |
+
+
+ |
+ h |
+ |
+
+
+
+Top-left to bottom-right are negative
+
+
+
+ |
+ |
+ c |
+
+
+ |
+ e |
+ |
+
+
+ g |
+ |
+ |
+
+
+
+
+
+ a |
+ |
+ |
+
+
+ |
+ |
+ f |
+
+
+ |
+ h |
+ |
+
+
+
+
+
+ |
+ b |
+ |
+
+
+ d |
+ |
+ |
+
+
+ |
+ |
+ i |
+
+
+
+Consider the same example as in method 2: matrix, which we will call B:
+
+
+
+ 1 |
+ 2 |
+ 3 |
+
+
+ 0 |
+ -3 |
+ 5 |
+
+
+ -10 |
+ 4 |
+ 7 |
+
+
+
+det(B) is given by the formula above. We apply the formula below:
+
+det(B) = 1 * (-3) * 7 + 2 * 5 * (-10) + 3 * 0 * 4 - 3 * (-3) * (-10) - 5 * 4 * 1 - 7 * 2 * 0, which we simplify to:
+
+det(B) = -21 - 100 + 0 - 90 - 20 - 0 = -231, same, as in method 1
+
+
#### More information:
* [Determinant of a Matrix](https://www.mathsisfun.com/algebra/matrix-determinant.html) on MathIsFun
* [3x3 Determinant calculator](http://www.wolframalpha.com/widgets/view.jsp?id=7fcb0a2c0f0f41d9f4454ac2d8ed7ad6)