Hi Grandad, Thanks for responding.
I did know those formulas and have been trying to work with them. I don't understand how you got the bottom on the right side to be that?
As far as I knew,
I thought that sin (a-b) could only be changed into sinacosb-sinbcosa using the sum and difference identities...
Am I missing something?
Hello aihal210Are you sure you are thinking of the correct formula? The one I've used there is sometimes called the 'Sum to Product' formula. You'll find some more information here.
Don't confuse this with . That's a different formula altogether (although it is one of the ones that is used to derive the Sum to Product formulae).
Grandad