Why do I get wrong values when I use the sin and cos functions?

Marcos · 02-29-2004, 08:53 PM

Like if I I put

Code:

double a = cos(45);

I get that a = .525322 when a should be = 7.07106. This happens with all thease kinds of funtions, whats happening?

BoredCrzy · 02-29-2004, 08:56 PM

a = .525322 because the function cos takes in radians rather than degrees (which should be .707106, not 7.07106)

MrWizard · 02-29-2004, 08:56 PM

Those functions take radians not degrees.

Marcos · 02-29-2004, 09:00 PM

duh! of course haha, Thanks a lot for the help guys

Marcos · 02-29-2004, 09:05 PM

oh and... so... like if I want to put cos(45°) (the degrees that you need 360 for a circle) how would I do it?

joshdick · 02-29-2004, 09:21 PM

You could write wrapper functions that do the conversions so that when you call them, you can always do it in degrees.

BoredCrzy · 02-29-2004, 09:47 PM

As Joshdick mentioned, write a wrapper function that converts the degree measure into radians (degree * PI/180)

e.g.

Code:

double sin_d (double degrees)
{
     return (sin(degrees * 3.1416/180));
}

02-29-2004, 08:53 PM	#1
Marcos Registered User Join Date: Jan 2003 Posts: 118	Why do I get wrong values when I use the sin and cos functions? Like if I I put Code: double a = cos(45); I get that a = .525322 when a should be = 7.07106. This happens with all thease kinds of funtions, whats happening? __________________ Why drink and drive when you can smoke and fly?
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02-29-2004, 08:56 PM	#2
BoredCrzy Registered User Join Date: Feb 2004 Posts: 6	a = .525322 because the function cos takes in radians rather than degrees (which should be .707106, not 7.07106)
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02-29-2004, 08:56 PM	#3
MrWizard Registered User Join Date: Apr 2002 Posts: 1,571	Those functions take radians not degrees. __________________ "...the results are undefined, and we all know what "undefined" means: it means it works during development, it works during testing, and it blows up in your most important customers' faces." --Scott Meyers
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02-29-2004, 09:00 PM	#4
Marcos Registered User Join Date: Jan 2003 Posts: 118	duh! of course haha, Thanks a lot for the help guys __________________ Why drink and drive when you can smoke and fly?
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02-29-2004, 09:05 PM	#5
Marcos Registered User Join Date: Jan 2003 Posts: 118	oh and... so... like if I want to put cos(45°) (the degrees that you need 360 for a circle) how would I do it? __________________ Why drink and drive when you can smoke and fly?
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02-29-2004, 09:21 PM	#6
joshdick Senior Member Join Date: Nov 2002 Location: Phildelphia, PA Posts: 1,146	You could write wrapper functions that do the conversions so that when you call them, you can always do it in degrees. __________________ FAQ "The computer programmer is a creator of universes for which he alone is responsible. Universes of virtually unlimited complexity can be created in the form of computer programs." -- Joseph Weizenbaum. "If you cannot grok the overall structure of a program while taking a shower, you are not ready to code it." -- Richard Pattis.
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02-29-2004, 09:47 PM	#7
BoredCrzy Registered User Join Date: Feb 2004 Posts: 6	As Joshdick mentioned, write a wrapper function that converts the degree measure into radians (degree * PI/180) e.g. Code: double sin_d (double degrees) { return (sin(degrees * 3.1416/180)); }
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