What rule is this? What is it called? Sin(2nX)/sin(nX) = 2Cos(nX)
Hello guest!
sin 2x = 2 sin x cos x is one of the double angle functions
sin(2X)=2sin(X)*cos(X)
One can show this nicely over an addition theorem:
sin(x+y) = sin(x) * cos(y) + sin(y) * cos(x)
and this case has to do with double angles ...
sin(2x) = sin(x+x) = sin(x) * cos(x) + sin(x) * cos(x) = 2*sin(x)*cos(x)
!
If I don't mind asking. Other than addition theorm what other rules do I need to learn, that is in the same level of learning, concerning sin and cos.
I'm abit behind in mathematics. I think half-angle trigonetric formulae is one of them.
Dear learner of trigonometry!
http://mathworld.wolfram.com/TrigonometricAdditionFormulas.html
Study this, please!
I wish you great success.
!