A Sine/Cosine Identity

A

0.2

B

0.7

B=A

This Demonstration looks at the trigonometric identity

sin(2θ)=2sin(θ)cos(θ)

. We plot the functions

sin(Ax)

(red curves),

cos(Bx)

(orange curves), and compare the plots of the functions

2sin(Ax)cos(Bx)

(black, on the left) and

sin((A+B)x)

(black, on the right); when

A=B

, they are the same.