Thread: proof of trig identity

am trying to prove that

Originally Posted by sigma1

am trying to prove that

Dear sigma1,

Try using the sum-to-product formula. Hope this will help you!!

i have tried but i seem to be getting no where with this one.

Originally Posted by sigma1

i have tried but i seem to be getting no where with this one.

Dear sigma1,

You can't be getting no where. Now use, for the numerator, and for the denominator.

Hope this will help you.

Hi sigma1,

if it looks confusing with "A" in both,
you can rewrite it as



where X=4A, Y=2A

and



When you work this out, you will have cancellation of terms in your fraction,
leading to the result.