Question

Qual a formula para calcularmos Cos 2x?

Answer 1

Cos 2x = Cos²x - Sen²x

Answer 2

Fórmulas da adição/subtração de arcos:

$\boxed{\boxed{sen(a\pm b)=sen(a)\cdot cos(b)~\pm~sen(b)\cdot cos(a)}}\\\\\\\boxed{\boxed{cos(a\pm b)=cos(a)\cdot cos(b)~\mp~sen(a)\cdot sen(b)}}\\\\\\\boxed{\boxed{tg(a\pm b)=\dfrac{tg(a)\pm tg(b)}{1\mp tg(a)\cdot tg(b)}}}$
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$cos(2x)=cos(x+x)\\\\cos(2x)=cos(x)\cdot cos(x)-sen(x)\cdot sen(x)\\\\\\\boxed{\boxed{cos(2x)=cos^{2}(x)-sen^{2}(x)}}$