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Question: Significant digits

Question:Significant digits

vvostri 56 Maple
constants
December 23 2008
0

Hello, I am new to Maple, and I have a novice question on rounding with evalf function.

 

I have an expression:

m:=(x,y)->126*cos(a)^2*(cos(x)-sin(x)*cos(y+b+c)*tan(a))-42;

 

Then I set some parameters as constants:

g:=x->x*Pi/180;

a:=g(58); b:=g(-45); c:=g(100);

 

And evaluate the function at x=0, y=0 with different number of significant digits:

n:=eval(m(0,0));

evalf4(n); evalf5(n);

Which returns -6.58 and -6.619.

 

-6.619 does not round to -6.58. Am I doing something wrong, or is it some intrinsic uncertainty with evaluations?

 

Thank you in advance!
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