Calculating values of trig functions

by Felix83
Tags: functions, trig, values
Felix83 is offline
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?
Phys.Org News Partner Mathematics news on
Researchers help Boston Marathon organizers plan for 2014 race
'Math detective' analyzes odds for suspicious lottery wins
Pseudo-mathematics and financial charlatanism
CrankFan is offline
Feb25-05, 10:15 AM
P: 135
Read this

or try a web search for "CORDIC."
Moo Of Doom
Moo Of Doom is offline
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]


[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 is offline
Feb26-05, 09:53 AM
Sci Advisor
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.
Moo Of Doom
Moo Of Doom is offline
Feb26-05, 12:48 PM
P: 367
Really? Strange... I was just told that... oh well.

Register to reply

Related Discussions
Absolute Values and Continuous Functions Calculus & Beyond Homework 1
Trig integrating with absolute values: Calculus & Beyond Homework 3
Computing Expectation values as functions of time. Advanced Physics Homework 18
What does it mean to find eigen values and functions of an infinite well? Advanced Physics Homework 1
Calculating values of the zeta function Linear & Abstract Algebra 2