1. ## Maths help???

Pretty easy I think but I was out sick when they did it in school and none of the trigonometric examples in my book cover this:

How does sin 2 a = 2sinacosa

2. what do you mean. what values of a satisfy(all of them) or a proof of the identity (use sin(x+y) = sinxcox + sinycosy)

3. Its a double angle identity. This is my only idea of how to prove it involves a sum to product function but I keep on running into dead ends.

4. maybe

2sin(a)cos(a)
2(1/2(sin(a+a)+sin(a-a))): product to sum formula
sin(2a)+sin(0)
sin(2a)+0
sin(2a)

thats the closest I can get

5. sin(x+x) = sinxcox + sinxcox = 2sinxcosx = sin(2x)

also i mistyped the identity in my first post its sinxcosy + cosxsiny

6. It's a proof of identity question.

7. Originally Posted by God
sin(x+x) = sinxcox + sinxcox = 2sinxcosx = sin(2x)

also i mistyped the identity in my first post its sinxcosy + cosxsiny
That looks right but it also looks way too simple to be the answer. Is there a way we can throw the sin rule/cosine rule/angle formula in the middle to prove of or something?

8. so lord, do I just not exist or something

9. Why do you want it to be complex, Lord? It has a very simple answer, that is the elegance of Math.

10. Everytime I see this thread I read it as Meths help

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