Calculating values of trig functions


by Felix83
Tags: functions, trig, values
Felix83
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#1
Feb25-05, 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?
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CrankFan
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#2
Feb25-05, 10:15 AM
P: 135
Read this

or try a web search for "CORDIC."
Moo Of Doom
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#3
Feb26-05, 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.

HallsofIvy
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#4
Feb26-05, 09:53 AM
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Thanks
PF Gold
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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.
Moo Of Doom
Moo Of Doom is offline
#5
Feb26-05, 12:48 PM
P: 367
Really? Strange... I was just told that... oh well.


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