Re: Trig identity oscillations

*To*: mathgroup at smc.vnet.net*Subject*: [mg47710] Re: Trig identity oscillations*From*: adam.smith at hillsdale.edu (Adam Smith)*Date*: Fri, 23 Apr 2004 02:30:38 -0400 (EDT)*References*: <c67q7l$gum$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

You are correct that Cos[t+5 Pi/6]/Sin[t+Pi/3] = 1. What is happening is that the Plot function is numerical. As is substitutes in various values for t you end up with a very small number divide by another very small number. The rounding that occurs in the numerical evaluations is what causes the unexpected behavoir. Try Simplify[Cos[t+5 Pi/6]/Sin[t+Pi/3]] and you will find that Mathematica returns the expected 1. In general it is useful to simplify any complicated function before plotting. Plot[Simplify[Cos[t+5 Pi/6]/Sin[t+Pi/3]],{t,0,2 Pi}] Adam Smith mathma18 at hotmail.com (Narasimham G.L.) wrote in message news:<c67q7l$gum$1 at smc.vnet.net>... > Should it not be a more placid -1 ? > Plot[Cos[t+5 Pi/6]/Sin[t+Pi/3],{t,0,2 Pi}]