## sqrt(x^2) = +x or -x ?...

Hi, I have a problem related to the cancellation of the square root with a square in its argument, see the image below.

Santiago

## Angle of a triangle in geom3d[FindAngle] ...

Why in geom3d[FindAngle] we cannot get the value of the angle of a triangle greater than Pi / 2?
For example, I build a chord of a circle of unit radius along the sides of the triangle and calculate the center angle that corresponds to the given angle of the triangle. But it's not very convenient.
TR_ANGLE.mw

## Circumscribed ellipse

by: Maple 17

One way to find the equation of an ellipse circumscribed around a triangle. In this case, we solve a linear system of equations, which is obtained after fixing the values of two variables ( t1 and t2). These are five equations: three equations of the second-order curve at three vertices of the triangle and two equations of a linear combination of the coordinates of the gradient of the curve equation.
The solving of system takes place in the ELS procedure. When solving, hyperboles appear, so the program has a filter. The filter passes the equations of ellipses based on by checking the values of the invariants of the second-order curves.
FOR_ELL_ТR_OUT_PROCE_F.mw  ( Fixed comments in the text  01, 08, 2020)

## An ellipse inscribed in a given triangle

by: Maple 17

An attempt to find the equation of an ellipse inscribed in a given triangle.
The program works on the basis of the ELS procedure.  After the procedure works, the  solutions are filtered.
ELS procedure solves the system of equations f1, f2, f3, f4, f5 for the coefficients of the second-order curve.
The equation f1 corresponds to the condition that the side of the triangle intersects t a curve of the second order at one point.
The equation f2 corresponds to the condition that the point x1,x2  belongs to a curve of the second order.
Equation f3 corresponds to the condition that the side of the triangle is tangent to the second order curve at the point x1,x2.
The equation f4 is similar to the equation f2, and the equation f5 is similar to the equation f3.
FOR_ELL_ТR_PROCE.mw
For example

## Why inequal plot like this?...

Hi there,

Can someone explain to me why is it happening? If smaller equal than coloured well, if smaller then just the equal line appears. Why?

with(plots);
dm1 := .23; pm12 := .7; dm12 := .23;
inequal(pm1*(dm12+am21)-pm12*(dm1+am21) <= 0, pm1 = 0 .. 1, am21 = 0 .. 1, color = "Nautical 1");

inequal(pm1*(dm12+am21)-pm12*(dm1+am21) < 0, pm1 = 0 .. 1, am21 = 0 .. 1, color = "Nautical 1")

Thank you!

## Colouring inequalities...

Hello everyone,

I would have a question about how to colour a region of complicated inequalities.

I'm curious about the region where my 'lambdas' are all negatives regarding the parameters 'pm2' and 'am2', but I always find difficulties even if I try with implicitplot or inequal commands. Also, I would like to put into the same graph with different colours when they are separately smaller than 0.

I've already tried plenty of things, I hopefully attached some pics by snipping tool about them.  And here is an example of my problem:

p61w:= implicitplot([lambda61 <= 0], pm2 = 0 .. 1, am2 = 0 .. 1)

in61 := inequal(lambda61 <= 0, pm2 = 0 .. 1, am2 = 0 .. 1)

display(in61,p61w)

So, the main issue that it is not just coloured where my condition is true, but elsewhere too. In plot 'in61' as you can see, there is a region approx. pm2=0..0.6 where it shouldn't be coloured since my condition is not true there. In the graph; 'display(in61, p61w)',  it is visible that under the red line should be just coloured however my 'inequal' command coloured it outside too.

Also, I tried with implicitplot, for example:

p6 := implicitplot([lambda61 <= 0], pm2 = 0 .. 1, am2 = 0 .. 1, filled = true, coloring = [blue, white], transparency = .5)

But the result is similarly wrong. And I'm not sure why it happens and how can I fix it.

(It's okay if for example for these particular lambdas (lambda61,lambda62) never negatives together, but I have more systems and I don't think it works properly)

I read similar questions too but I couldn't find an answer so, I would very appreciate any suggestions.

This is my first post in Maple, so please let me know if I have mistaken something.

## Is it possible to insert text above and next to a ...

Is it possible to make notes above and next to a matrix like in the image above? How?

I'm sorry if this is really obvious but I'm new to Maple.

Thank you in advance :)

## A triangle of maximum area inscribed in an ellipse...

by: Maple 17

One of the forums asked a question: what is the maximum area of a triangle inscribed in a given ellipse x^2/16 + y^2/3 - 1 = 0? It turned out to be 9, but there are infinitely many such triangles. There was a desire to show them in one of the possible ways. This is a complete (as far as possible) set of such triangles.
(This is not an example of Maple programming; it is just an implementation of a Maple-based algorithm and the work of the Optimization package).
MAX_S_TRIAN_ANINATION.mw

## Cannot open Incomplete Worksheet...

Problems with incomplete worksheet.

I have saved a .mw worksheet, which i cannot open in Maple, and i get an error code:
"There were problems during the loading process. Your worksheet may be incomplete"

I have attached a link, where a user is helped with the same problem, but i cannot understand the solution there has been given:

https://www.mapleprimes.com/questions/125503-Incomplete-Worksheet

I have attached the worksheets, and would be so gratefull for any help:

Best regards

Henrik Jorgensen

## Error, numeric exception: division by zero...

Error, numeric exception: division by zeroprpblem_maple_2.mw

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## Нoles on an implicit plot

by: Maple 17

A way of cutting holes on an implicit plot. This is from the field of numerical parameterization of surfaces. On the example of the surface  x3 = 0.01*exp (x1) / (0.01 + x1^4 + x2^4 + x3^4)  consider the approach to producing holes. The surface is locally parameterized in some suitable way and the place for the hole and its size are selected. In the first example, the parametrization is performed on the basis of the section of the initial surface by perpendicular planes. In the second example, "round"  parametrization. It is made on the basis of the cylinder and the planes passing through its axis. Holes can be of any size and any shape. In the figures, the cut out surface sections are colored green and are located above their own holes at an equidistant to the original surface.
HOLE_1.mwHOLE_2.mw

## Moving boundary and Differential transformation me...

How to solve this DE by using  Differential transformation method?

diff(f(x),x\$3)+1/2 * f(x) *diff(f(x),x\$2)=0;

with boundary conditions

f(0)=1 ; f '(0)= lamda * f ''(0)   and   f ' (x) -> 1  as x -> infinity
where lamda is some constant...

## Fractional order and differential transformation m...

How to solve this DE with IC by using DTM.
D^m u(x,t)=u''(x,t)-u^2 (x,t), where n-1< m < n

IC: u(x,0)=1+sin(x), and u'(x,0)=0