Respuesta :

ghanami

Answer:

Step-by-step explanation:

hello :

sin(x+y)= sinxcosy+cosxsiny...(*)

sin(x-y)= sinxcosy-cosxsiny....(**)

add (*) and(**) : sin(x+y)+sin(x-y)= 2sinxcosy

1/2(sin(x+y)+sin(x-y)) = sinxcosy......true

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