diff --git a/src/content/docs/maths/matrices/14-eigenvalues-eigenvectors.md b/src/content/docs/maths/matrices/14-eigenvalues-eigenvectors.md index 66b5f8e..f2f49d1 100644 --- a/src/content/docs/maths/matrices/14-eigenvalues-eigenvectors.md +++ b/src/content/docs/maths/matrices/14-eigenvalues-eigenvectors.md @@ -21,8 +21,11 @@ Roots of the equation $p(\lambda) = 0$ are the eigenvalues of $A$. :::note -- [Determinant of a matrix](/maths/matrices/determinant/#in-relation-with-eigenvalues) - can be written in terms of all of its eigenvalues. +- Product of the eigenvalues is equal to the + [determinant](/maths/matrices/determinant/#in-relation-with-eigenvalues) of + the matrix +- Sum of the eigenvalues is equal to the [trace](/maths/matrices/trace) of a + matrix - If $\lambda$ is an eigenvalue of $A$, then $\lambda^2$ is an eigenvalue of $A^2$ - $A$ and $A^T$ have the same eigenvalues. diff --git a/src/content/docs/maths/riemann-integration/17-gamma-function.md b/src/content/docs/maths/riemann-integration/17-gamma-function.md index c0209d5..4560928 100644 --- a/src/content/docs/maths/riemann-integration/17-gamma-function.md +++ b/src/content/docs/maths/riemann-integration/17-gamma-function.md @@ -138,12 +138,14 @@ $\ln$, it's better to try this substitution. ### Form 4 +For $k\in \mathbb{R}$: + ```math -\Gamma(n) = 2 \int_0^\infty e^{-x^2} x^{2n-1}\,\text{d}x +\Gamma(n) = k \int_0^\infty e^{-x^k} x^{kn-1}\,\text{d}x ``` :::note[Proof Hint] -Use $x=t^2$. $ $ +Use $x=t^k$. $ $ ::: diff --git a/src/content/docs/maths/vectors/03-straight-lines.md b/src/content/docs/maths/vectors/03-straight-lines.md index e66058b..cb381a6 100644 --- a/src/content/docs/maths/vectors/03-straight-lines.md +++ b/src/content/docs/maths/vectors/03-straight-lines.md @@ -95,15 +95,21 @@ Using the $\alpha,\beta$ lines mentioned above: $ $ Here $v_1, v_2$ are $2$ vectors parallel to $\alpha, \beta$ respectively. -## Shortest distance to a point +## Shortest distance from a point -Suppose $x_1$ and $x_2$ lie on a line. Shortest distance to the point $P$ is: +The distance can be calculated using Pythogoras' theorem. ```math d^2 = -\frac{ -\bigg|(\underline{x_2} - \overrightarrow{OP}) \times (\underline{x_1}-\overrightarrow{OP})\bigg|^2 -}{ -\big|\underline{x_2} - \underline{x_1}\big|^2 -} +{\big\lvert\underline{r} - \underline{p}\big\rvert}^2 - +\bigg[ +\frac{\underline{n}\cdot (\underline{r} - \underline{p})}{\lvert \underline{n} \rvert} +\bigg]^2 ``` + +Here: + +- $P$ is the arbitrary point +- $\underline{p}$ is the position vector of $P$ +- $\underline{r}$ is the position vector of a point on the line +- $\underline{n}$ is parallel to the line diff --git a/src/content/docs/maths/vectors/04-planes.md b/src/content/docs/maths/vectors/04-planes.md index a994764..5fc9a84 100644 --- a/src/content/docs/maths/vectors/04-planes.md +++ b/src/content/docs/maths/vectors/04-planes.md @@ -77,16 +77,16 @@ The angle between the planes $\phi$ is given by: $ $ Here $\underline{n_A},\underline{n_B}$ are normal to the planes $A,B$. -## Shortest distance to a point +## Shortest distance from a point -Considering a plane $ax+by+cz=d$.$ $ +Consider the plane $ax+by+cz=d$.$ $ ```math \text{distance}= \frac{ -\lvert +\big\lvert (\underline{r_1}-\underline{r_0})\cdot\underline{n} -\rvert +\big\rvert }{ \lvert{\underline{n}}\rvert } @@ -94,4 +94,29 @@ Considering a plane $ax+by+cz=d$.$ $ - $\underline{n}$ is a normal to the plane - $\underline{r_0}$ is the position vector of any known point on the plane -- $\underline{r_1}$ is the position vector to the arbitrary point +- $\overline{r_1}$ is the position vector to the arbitrary point + +## Intersection + +In 3D, to prove 2 planes intersect, it has to be proven that there is a point +satisfiying both of the planes. + +### Of 2 planes + +Can either be a: + +- Plane - when the planes coincicde +- Line - otherwise + +Equation of the line of intersection can be found by: + +- Solving $y,z$ with respect to $x$ +- Subject $x$ and symmetric form can be found + +### Of 3 planes + +Can either be a: + +- Plane - when the planes coincide +- Line +- Point diff --git a/src/content/docs/maths/vectors/05-skew-lines.md b/src/content/docs/maths/vectors/05-skew-lines.md index 1491f1f..a5eb2b3 100644 --- a/src/content/docs/maths/vectors/05-skew-lines.md +++ b/src/content/docs/maths/vectors/05-skew-lines.md @@ -59,5 +59,5 @@ a_1,b_1,c_1 Here -- $\underline{n}$ is the normal to both $l_1,l_2$ +- $\underline{n}$ is the unit normal to both $l_1,l_2$ - $A$ and $B$ are points lying on each line