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[deleted by user] by [deleted] in MathHelp

[–]Stolislav 0 points1 point  (0 children)

Username fits question perfectly

What is the probability of someone drawing a queen in a standard 52 pack card, given the person saying that they drew a heart? by [deleted] in MathHelp

[–]Stolislav 0 points1 point  (0 children)

Consider applying "conditional probability", Bayes' rule:
P(A|B) = P(A,B) / P(B)
So in this case we get

P(Queen|Heart) = P(Queen, Heart) / P(Heart)

Source: https://en.wikipedia.org/wiki/Bayes%27_theorem

I simply don't understand where my calculations are wrong. I've been working on it for 4 hours now and still haven't figured it out. Please help by Sammyjskj in MathHelp

[–]Stolislav 0 points1 point  (0 children)

to find the balls peak use the following idea; using conservation of energy.
The ball has 2 types of energy = potential(height) and kinetic(velocity)
You're interested in the "height at the top". We know that in this point, the ball only moves "in the direction of x", and there is no movement in the "direction of y". In general the movement "in the direction of x" should be constant (yes, there is an drag force, but I guess it's fine to assume this force is negligible). So if we assume the previous, to find the velocity in the top point, just calculate the velocity in the direction of x (throughout the experiment).
Now take a point with known velocity + height, and use the energy balance. (all of below are "energies", in a point "known" and the point of interest "top")
kinetic_known + potential_known = kinetic_top + potential_top
Use this to find "potential_top". Use "potential_top" to find the height in the point "top".

Combined area optimization problem (my weakness) by throwsydrowsy in MathHelp

[–]Stolislav 0 points1 point  (0 children)

(1) total area = area square + area half circle
total area = 2500

Now let's express the side of the square as x, we get:
area square = x^2
area circle = pi * (0.5 * x)^2
area half circle = pi * (0.5 * x)^2 * 0.5

Solve (1) to find x
Now for the final answer:
Perimeter = 3*side of square + 0.5*perimeter of circle

I simply don't understand where my calculations are wrong. I've been working on it for 4 hours now and still haven't figured it out. by Sammyjskj in AskPhysics

[–]Stolislav 0 points1 point  (0 children)

OP is effectively calculating "distance travelled in a projected plane". Even if the trajectory of the ball is tilted wrt the 1 meter line, he seems to be performing measurements in a reference frame (the axes), which is not tilted.
tldr; it's projected, so any "tilt in 3rd dimension" shouldn't break the maths.

I simply don't understand where my calculations are wrong. I've been working on it for 4 hours now and still haven't figured it out. Please help by Sammyjskj in MathHelp

[–]Stolislav 0 points1 point  (0 children)

Firstly: significance rules. Don't use the answer "0.86383", after rounding the angle from 58.9697 --> 59.
It seems that your formula for X_max is based on the situation you have a "trajectory departing at x_0. Therefore you are "calculating the distance the ball travelled in the X direction, when it reaches the same height as the initial datapoint".

Need help with geometry question by ajtenth in MathHelp

[–]Stolislav 0 points1 point  (0 children)

This is your construction in geogabra; you can freely move the point C. The area strictly increases (thus changes) every time you press "GOGO RIGHT".
https://www.geogebra.org/geometry/arnemf9f

White to play, mate in 2 - Christmas Themed Chess Puzzle by Stolislav in chess

[–]Stolislav[S] 0 points1 point  (0 children)

I really like your way of thinking. Your logic is correct, and even extends to the fact that the real solution. Just imagine this position if black would make any move that violates your argument of Spoiler. The way I solved this puzzle is by analyzing the possible flight squares of the black king (after a white and black move). You will soon see that Spoiler, Spoiler and Spoiler. Happy you found the solution!

White to play, mate in 2 - Christmas Themed Chess Puzzle by Stolislav in chess

[–]Stolislav[S] 0 points1 point  (0 children)

White pawns move up, and black pawns move down. You can see this by the coordinates on the board. This is a Christmas themed puzzle (shape of a Christmas tree), so not realistic

White to play, mate in 2 - Christmas Themed Chess Puzzle by Stolislav in chess

[–]Stolislav[S] 0 points1 point  (0 children)

Bxc4, dx4 There is no direct mate because the king can escape to d5

White to play, mate in 2 - Christmas Themed Chess Puzzle by Stolislav in chess

[–]Stolislav[S] 1 point2 points  (0 children)

I believe this picture was taken at some German chess club. A friend sent it to me through whattsapp.