violetblue253
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Does anyone know how to solve this
(a) Write down formulae for sin (A + B) and sin (A – B).

Using X = A + B and Y = A – B, prove that
sin X + sin Y = 2 sin(X+Y/2) cos (X+Y/2)

I'm super confused? Thanks
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davros
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(Original post by violetblue253)
Does anyone know how to solve this
(a) Write down formulae for sin (A + B) and sin (A – B).

Using X = A + B and Y = A – B, prove that
sin X + sin Y = 2 sin(X+Y/2) cos (X+Y/2)

I'm super confused? Thanks
They're asking you to derive the sum-to-product formulae from formulae you already know

Can you do the first part - expand sin(A+b) and sin(A-B) ?
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violetblue253
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(Original post by davros)
They're asking you to derive the sum-to-product formulae from formulae you already know

Can you do the first part - expand sin(A+b) and sin(A-B) ?
Yeah I did that and I got
sin X + sin Y = 2sinAcosB + cosAsinB - cosAsinB
sin X + sin Y = 2sinAcosB
idk what to do after that though
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davros
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(Original post by violetblue253)
Yeah I did that and I got
sin X + sin Y = 2sinAcosB + cosAsinB - cosAsinB
sin X + sin Y = 2sinAcosB
idk what to do after that though
Well if X = A + B and Y = A - B, can you solve these as if they were simultaneous equations to write A = something in terms of X and Y and the same for B?
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violetblue253
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(Original post by davros)
Well if X = A + B and Y = A - B, can you solve these as if they were simultaneous equations to write A = something in terms of X and Y and the same for B?
Got it thank you!!
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