Question

Sendo senX= 3/5, então cosX vale:

Answer 1

Utilizando a identidade trigonométrica    sen²x + cos² = 1  :

$\left(\frac{3}{5}\right)^2~+~cos^2x~=~1\\\\\\\frac{9}{25}~+~cos^2x~=~1\\\\\\cos^2x~=~1-\frac{9}{25}\\\\\\cos^2x~=~\frac{16}{25}\\\\\\cos(x)~=~\sqrt{\frac{16}{25}}\\\\\\\boxed{cos(x)~=~\frac{4}{5}}$

Answer 2

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Formula

$Sen^2x+cos^2x=1$

onde:

Senx=$\frac{3}{5}$

substituindo teremos:

$(3/5)^2+cos^2x=1$

$9/25$+cos^2x=1[/tex]

$cos^2=1-9/25$

$cos^2x=25-9/25$

$cos^2x=16/25$

cosx=√(16/25)

$cosx=4/5$