Trig functions in CAS

01242015, 05:47 PM
Post: #1




Trig functions in CAS
Working with some trigonometric expressions, I want to rewrite sin(6x) to sin(3x+3x)=2*cos(3x)*sin(3x)
How can I do that with the Prime ? 

01272015, 01:16 PM
Post: #2




RE: Trig functions in CAS
You probably just have to play around the CAS commands. I don't think there is a built in function that breaks down sin(6x) to sin(3x + 3x).
The trigexpand command will expand such expressions as cos(nx) and sin(nx) into a polynomial. Using tcollect I was able to go the other way: tcollect(2*sin(3x)*cos(3x)) > sin(6x) trigexpand(sin(6x)) > (32*cos^5 x  32*cos^3 + 6*cos x)*sin x 

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