Trig Proof Question (1 Viewer)

[Hehehe22]

I'm so confused, I'm using sum-to-product formulae for this question but I keep getting the negative version of the RHS, because I thought that cosA - cosB = -2sin......, unlike the solution which uses the positive form (as highlighted). I feel like I'm being silly but I can't figure it out. Anyone able to help?

 

[alphxreturns]

 

[Hehehe22]

View attachment 48669

Ok yeah I was dumb. But I still don't get how they're using the sum-to-product formula, even if it's not the best way

 

[melanie_o]

I'm so confused, I'm using sum-to-product formulae for this question but I keep getting the negative version of the RHS, because I thought that cosA - cosB = -2sin......, unlike the solution which uses the positive form (as highlighted). I feel like I'm being silly but I can't figure it out. Anyone able to help?

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If I get this tomorrow, I'll just take one for the team

 

[melanie_o]

I'm still trying to learn logistic equations fmlllll

 

[alphxreturns]

Ok yeah I was dumb. But I still don't get how they're using the sum-to-product formula, even if it's not the best way

View attachment 48670

yeah im also not sure why theyd do that. they went to the trouble of flipping the α and β too to get rid of the negative