
#1
Feb2505, 10:06 AM

P: 75

How does a calculator approximate a trig function. For example, you punch in sin(37deg) and the calculator will give you 0.6018150232. how does it figure this out?




#2
Feb2505, 10:15 AM

P: 135




#3
Feb2605, 03:08 AM

P: 367

Calculators use partial sums of power series to approximate sine and cosine.
The power series for sine is: [tex]sin(x) = x  \frac{1}{3!} * x^{3} + \frac{1}{5!} * x^{5}  \frac{1}{7!} * x^{7} + ...[/tex] Cosine: [tex]cos(x) = 1  \frac{1}{2!} * x^{2} + \frac{1}{4!} * x^{4}  \frac{1}{6!} * x^{6} + ...[/tex] I'm not sure how many terms they usually use, but that doesn't really matter. The more terms, the more accurate. 



#4
Feb2605, 09:53 AM

Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 38,881

Calculating values of trig functions
Moo Of Doom: I thought for a long time that calculators used power series but I've been told that is not true. Check out CranFan's suggestion about the CORDIC algorithm.




#5
Feb2605, 12:48 PM

P: 367

Really? Strange... I was just told that... oh well.



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