10286 - Trouble with a Pentagon

[Almost Human]

What are we looking for actually ???

can I use the height of the pentagon to define the side length ???

code :

Code: Select all

#include <math.h>
#include <stdio.h>

int main ( void )
{
	long double s , output , pi = 3.1415926535897932384626433832795 ;

/*	freopen ( "10286.in" , "r" , stdin ) ;
	freopen ( "10286.out" , "w" , stdout ) ;*/

	while ( scanf ( "%Lf" , &s ) != EOF )
	{
		output = ( s * sin ( 36 * pi / 180 ) + s * cos ( 18 * pi / 180 ) ) / sqrt ( 2 ) ;

		printf ( "%.10Lf\n" , output ) ;
	}

	return 0 ;
}

[hujialie]

To Almost Human:

You should notice that the low point of the square is a bit higher than the
horizontal line,so you can't calculate the diagonal of the square by the height of pentagon and,of course ,the side of square.

Try to solve it from another angle----using sine theorem(I am not sure whether it should say so),i.e.,the theorem pointing out the relationship between the edge and angle of a triangle.

If you want some test data,mailto me.
Good luck.

[anupam]

Would you please leave a bit more discussion to solve the problem?
Anupam

[Raiyan Kamal]

This problem can be solved without taking the height in concideration. Think about the triangle that is formed when the prntagon is touching the two adjacent sides of the sqr.

Dear Anupam bhai, sine rule ( as we were taught in school ) can be used to solve this

[anupam]

Ha ha,
this is the ever smallest program from me (just 2 lines).
Thanks Raiyan Kamal. Sometimes, very easy problem seems tough to me.
Thanks again.

[stcheung]

Isn't the answer of the form F * sin(a) / sin (b)?

I calculated values for a & b, but the result is different from output. I then used brute-force to come up with values for (a, b) that would yield sample output, but these all got me WA. Any idea? Can somone provide more output? Thanks.

[sefakilic]

Hello,

I am getting Presentation Error.
What can be the reason?

Code: Select all

REMOVED

Thanks.

edit: It seems ACCEPTED now. :s

-- sefa kilic

[Asma_ju]

Code: Select all

sside=pside/sin(108*PI/180);
        cout<<setprecision(10)<<fixed<<sside<<endl;

Is this logic correct?
If wrong may anyone can give some idea or test case?