## 55 Reputation

10 years, 332 days

## Select from a lists of lists...

Maple 2019

Hi everybody and thank you all in advance.

This is my question. Suppose I have a list of lists like this:

[[1,2,3],[7,8,9],[13,12,11]]

I want to select all 3rd element from the list of lists and get:

[3,9,11]

Another example:

[1, [2, 3], [4, [5, 6], 7], [8, 3], 9] and select the first element from the list of lists and get:

[1, 2, 4, 8, 9]

Additionally suppose I want to sort a list of lists but base on the 3rd element of every sublist. Example:

From this list:

[[1,2,3],[7,8,2],[13,12,1]] sorted by the  3rd element I would get:

[[13,12,1], [7,8,2], [1,2,3]]

## solve with conditionals...

Maple 2019

As always, thank you all in advanced.

I found this challenge by chance.

solve 615+x^2=2^y over integers.

I rushed to Maple and tried to solve it  with “solve” and "assuming" but I did not get results.

solve(615+x^2=2^y) assuming x::integer,y::integer   did not work.

How could this equation be suitably formulated for Maple to solve it?

## Remainder of two terms with Pi...

Maple

Hi everyone. Thank you all in advance.

My question: is there a function for quotient and reminder for something like:

(22*Pi/3, Pi/2)

I tried frem, rem, quo. Neither of them worked.

## How to solve sin of x degree equal to si...

Maple

Hello everybody and thankyou in advance to answer my question.

I am trying to answer this question:

“Find the solutions for x so that the sine of x degrees be equal to the sine of x radians in the interval [0, Pi].” I wrote this formula to solve it but without success:

solve(sin(x*degree)=sin(x),x) assuming 0<=x<=Pi

I expected a solution like:

{x=0, x=(180*Pi)/(180+Pi)} but not,

I somehow get a numeric solution for the first positive real number within the referred interval with this:

fsolve(sin(x*Pi/180) = sin(x), x, 0 .. Pi);

But if I change the interval for example [0, 3*Pi] I still only get one answer, not the four I spect.

## map a list of functions expecting two in...

Maple 2018

Hi there. Thank you all in advanced.

The general question is how to pass a pair of values to a list of functions that expect that pair of values as input.
I already know this solution for passing a list of values to a list of functions that expect one value as input.

map(eval~,[f(x),g(x)],x=~[p,q,t])

Well f(x) and g(x) take every element of the list, but what if f(x) and g(x) expect two values. The concrete case is to pass p and q to iquo and irem. The following were my tries:

• map(eval~,[iquo(x),irem(x)],x=[p,q])
• map(eval~,[iquo(x),irem(x)],x=(p,q))
• map(eval~,[iquo(op(x)),irem(op(x))],x=[p,q])

I searched and found some partial related topics in the site but not quite with this approach.

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