 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Math Forum / Mathematics / Undergraduate Math / July 2007Simplify cos(x+pi)
Simplify cos(x+pi) How do I do this with the addition/subtraction formula? On Thu, 26 Jul 2007 20:33:05 -0700, in alt.math.undergrad: > Simplify cos(x+pi) > How do I do this with the addition/subtraction formula? The sum formula for the cosine is cos(x + y) = cos(x) cos(y) - sin(x) sin(y), so cos(x + pi) = cos(x) cos(pi) - sin(x) sin(pi). You know what cos(pi) and sin(pi) are, so you can substitute those values into this formula to complete the simplification. Brian Thu, 26 Jul 2007 23:48:32 -0400 from Brian M. Scott <b.scott@csuohio.edu>: > On Thu, 26 Jul 2007 20:33:05 -0700, > in alt.math.undergrad: [quoted text clipped - 4 lines] > > cos(x + pi) = cos(x) cos(pi) - sin(x) sin(pi). And you can check your work by thinking about what relation cos(x+pi) must bear to cos(x). Since an angle of pi is half a circle, what geometrical relationship do you see between cos(x+pi) and cos(x)? Work this out on your own, and then jave a look at my less-than- beautiful diagram at http://oakroadsystems.com/twt/refangle.htm#RelatedIdentities  Signature"The internet is famously powered by the twin engines of bitterness and contempt." -- Nathan Rabin, /The Onion/ Stan Brown, Oak Road Systems, Tompkins County, New York, USA http://OakRoadSystems.com/ >Simplify cos(x+pi) > >How do I do this with the addition/subtraction formula? The sum of two angles formula is cool, but here is another method. cos(x + pi) = cos[(x + pi/2) + pi/2] = - sin(x + pi/2) = - cos x This only works for specific angles because cosine is "complementary" sine. Brian > >Simplify cos(x+pi) > > [quoted text clipped - 3 lines] > > cos(x + pi) = cos[(x + pi/2) + pi/2] = - sin(x + pi/2) = - cos x You may find that the op wants to apply the addition formula to cos[(x + pi/2) + pi/2]! SignatureRemove "antispam" and ".invalid" for e-mail address. "He that giveth to the poor lendeth to the Lord, and shall be repaid," said Mrs Fairchild, hastily slipping a shilling into the poor woman's hand. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2010 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.