trig/calc question

Raven · 06-12-2006, 10:52 PM

It's been a while since I took trig and calc.
I know that...
sin(x) dx = cos(x)
cos(x) dx = -sin(x)

but, remind me...
-sin(x) dx = ?? -cos(x) ?
-cos(x) dx = ?? sin(x) ?

Thanks

Katon · 06-12-2006, 11:09 PM

-sin(x)dx=-(sin(x) dx)=-cos(x). Multiplying by constants - such as -1 - doesn't change a differential equation.

Craptacular · 06-12-2006, 11:17 PM

I think your original assumption is wrong. Isn't cos the derivative of sin, not the antiderivative? It should be d/dx sin(x) = cos(x)

Raven · 06-12-2006, 11:43 PM

That's what I was saying. Though maybe my syntax was wrong.

the derivative of sin(x) is cos(x) is what I was trying to write.

terpkristin · 06-13-2006, 02:22 PM

The way I always remembered it was:
S
C
-S
-C

For the derivative, you move down, for the integral, you move up.
I.e. d/dx sin(x) = cos(x)
d/dx cos(x) = -sin(x)
d/dx -sin(x) = -cos(x)

This is what Katon said, I just wanted to give you a memory aid.

/tk

PackerFanatic · 06-13-2006, 02:24 PM

Wow, and I had almost forgot why I hated trig and calc...now I remember...

*head hurts*

finkenst · 06-13-2006, 03:51 PM

Quote:

Originally Posted by PackerFanatic

Wow, and I had almost forgot why I hated trig and calc...now I remember...

*head hurts*

here here

06-13-2006, 02:22 PM	#5
terpkristin Grizzled Veteran Join Date: May 2003 Location: Ashburn, VA	The way I always remembered it was: S C -S -C For the derivative, you move down, for the integral, you move up. I.e. d/dx sin(x) = cos(x) d/dx cos(x) = -sin(x) d/dx -sin(x) = -cos(x) This is what Katon said, I just wanted to give you a memory aid. /tk __________________ GO TERPS! https://www.flickr.com/photos/terpkristin https://twitter.com/terpkristin

06-13-2006, 02:24 PM	#6
PackerFanatic Pro Starter Join Date: Jul 2005 Location: Appleton, WI	Wow, and I had almost forgot why I hated trig and calc...now I remember... head hurts __________________ Commissioner of the RNFL

06-12-2006, 11:09 PM	#2
Katon College Benchwarmer Join Date: Mar 2003 Location: Providence, RI	-sin(x)dx=-(sin(x) dx)=-cos(x). Multiplying by constants - such as -1 - doesn't change a differential equation.

06-12-2006, 11:17 PM	#3
Craptacular College Starter Join Date: Oct 2001 Location: The Mad City, WI	I think your original assumption is wrong. Isn't cos the derivative of sin, not the antiderivative? It should be d/dx sin(x) = cos(x)

06-12-2006, 11:43 PM	#4
Raven College Prospect Join Date: Oct 2000 Location: Baltimore, MD	That's what I was saying. Though maybe my syntax was wrong. the derivative of sin(x) is cos(x) is what I was trying to write.

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