calculating the area of a circle with bc

[Karl Larsen]

On 03/28/2010 01:51 PM, Tony Arnold wrote:
> Rei,
>
> Rei Shinozuka wrote:
>    
>> The area is proportional to the square of the diameter or radius.
>>
>> Data form www.dominos.com:
>>
>> Domino's 10" pizza is $7.00
>> Domino's 14" pizza is $11.99.
>>
>> The 10" price/diameter is 70 "cents per inch."
>> The 14" price/diameter is 85 "cents per inch."
>>
>> implying that the 10" is a better buy.
>>
>> But price/area shows:
>>
>> The 10" price/area is 8.6 cents per square inch.
>> The 14" price/area is 7.7 cents per square inch.
>>
>> The 14" pizza is 10% cheaper than the 10" pizza.
>>
>> For a pure comparisons, you are correct: coefficients like pi are not
>> needed to compare.  But you need to square the linear size of the pizza.
>>      
> I stand corrected again. And I thought I was good at maths!
>
> Regards,
> Tony.
>
>    
>> On 03/28/2010 03:24 PM, Tony Arnold wrote:
>>      
>>> Jozsef,
>>>
>>> Since the area of a pizza is directly proportional to its diameter, you
>>> only really need to calculate the price/diameter to find out the best
>>> value for money!
>>>
>>> Regards,
>>> Tony.
>>>
>>> Jozsef Vadkan wrote:
>>>
>>>        
>>>> input like:
>>>>
>>>> sh count.sh 0.45 2200
>>>> ...
>>>>
>>>> explanations:
>>>> 0.45 =>   diameter [in meter]
>>>>
>>>> 2200 =>   e.g. xy money
>>>>
>>>> $(echo "scale=100; 2^($1/2) * $(echo "scale=100; 4*a(1)" | bc -l)" | bc
>>>> -l) =>   area of the circle
>>>>
>>>> xy money =>   some nations currency
>>>>
>>>>
>>>> i'm dividing the area of the circle because i want to get the "xy
>>>> money/square meter"
>>>>
>>>>
>>>> #!/bin/bash
>>>>
>>>> echo "$2/$(echo "scale=100; 2^($1/2) * $(echo "scale=100; 4*a(1)" | bc
>>>> -l)" | bc -l)" | bc -l
>>>>
>>>>
>>>> is there a shorter/better way?
>>>>
>>>>
>>>> it would be a pizza price calculator. [:D]
>>>>
>>>> 45 cm pizza = 2200 xy money
>>>> 30 cm pizza = 1260 xy money
>>>> 22 cm pizza = 960 xy money
>>>>
>>>> i just want to count that, what will i have to choose to get the best
>>>> price for "xy money/square meter" pizza.
>>>>
>>>> don't laugh. [:D]
>>>>
>>>>
>>>>
>>>>          
>>>
>>>        
>>
>>      
> 		The area of a circle comes from pi r squared = pi (d/2) squared. How you do this with bc is not known to me but the formula is above and I can prove it.

73 Karl