Which expression is equivalent to sin(0.6x)−sin(0.4x)?

Use the following facts:

 

sin(a + b) = sin(a)cos(b) + sin(b)cos(a)

sin(a - b) = sin(a)cos(b) - sin(b)cos(a)

 

and set a = 0.5x, b = 0.1x

 

 to show that  sin(0.6x) - sin(0.4x) → 2sin(0.1x)cos(0.5x)

 

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