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Hi,
How would I solve this question:
express sinx sin(2x) + cosx cos(2x) in terms of cosx
I am really stuck in this.
Danny
Sinx*Sin2x + Cosx*Cos2x
= Sinx[Sin(x+x)] + Cosx[(Cos(x+x)]
= Sinx[2SinxCosx]+ Cosx[Cos²x - Sin²x]
Rearranging the terms,
= Cosx[2Sin²x + Cos²x - Sin²x]
= Cosx[Sin²x + Cos²x]
=Cosx (since Sin²x + Cos²x=1).
It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.
Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.
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How very elegant and unexpected.
Why did the vector cross the road?
It wanted to be normal.
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what do you mean? is it not right
No, it's right. It's just that I wouldn't have thought that such a complicated expression could be simplified into such a simple one like that.
Why did the vector cross the road?
It wanted to be normal.
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