Proposals of math codes. Area polygon. Vertices rectangle. Linear regression. Decimal IP

Hi, with this apk is possible calculate a integral of a real number? for example int(0,74)? tks

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This is an integral


24.- Calculate PI.

Create an app to calculate the value of PI with many decimals.

The output should be a decimal sequence beginning 3.14159265 ...

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25.- Find the division between two numbers by repeatedly subtracting the dividend minus the divisor.
Example: 22 / 4

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hello, great demonstration !!!
if I take your first example on calculating the area of a polygon, is it possible to color it?
what is the method (I am not as efficient as you in this field, I would even say beginner :-))
Thanks for reading

perhaps see here:

Canvas flood fill an area by Scott Ferguson.
Flood fill an image, extension.

A post worth bookmarking, not just for App Inventor but also if you need help with Maths :upside_down_face: :sweat_smile:

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26.- Cistercian Numerals.

Write a decimal number from 1 to 9999 and convert it into a Cistercian number.

Cistercian number:


p91G_cisterciensesi.aia (19.3 KB)
[not finished. It contains the 36 images of the symbols, with a transparent background.]


Did you watch this? :grin:


27.- Find the crossing point of two lines perpendicular to two sides of an equilateral triangle.

apk file in external link:

We have an equilateral triangle whose sides are 100.
On the left side we draw a segment of 65 and on the right side another of 47.
Find the equation of the line that passes through these points and is perpendicular to the sides.
Find the point where these lines intersect.


This triangle is used in various problem domains, from describing earth samples based on their proportions of sand, clay, and silt (a recent question on this forum) to choosing newly created character attribute values in the game Fallout 4 (according to my son (I haven't reached that game yet.))

The equilateral triangle has the interesting property that any point within the triangle's closest distances to the the three sides always add up to the same number, the height of the triangle.

Unfortunately, no source code is here, so we have to derive the equations from scratch.


Viviani's theorem


28.- Mathematical proposal for Pi day.

A circle has radius 7. We draw a radius at 30º and another at 31º, as the schematic figure indicates.

a) Find the value of the segment s.
b) What is the sum of the 360 ​​segments s drawn on the circle?
c) What value do we obtain by dividing the previous sum by the diameter of the circle?

d) Carry out the previous sections when the radius are 0.1º apart.


29.- Abacus Clock.

This "Abacus Clock" application indicates the actual time: HHMMSS.
It is a good idea to do it with App Inventor.

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30.- Validate Credit Card.

Write an application where the user enters a credit card number and shows if that card is valid or not.

Use the Luhn algorithm:


Can you please tell where can I download extension?

com.KIO4_AreaVerticeLinear.aix (7.2 KB)

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Thank you @Juan_Antonio
I tried to find in your website before I posted. But could not find the extension!.
Thanks for your help.

31.- Optical. Calculation of the scale of an image (beta).

Build an app where you enter the height of the image (G), the distance between the image and the axis of the lens (gw) and the focal length of the lens (f), and obtain the height of the projected image (B ) and the image scale (beta = B / G)

Simulator online (move Focus').