Question

utilizando a relação fundamental da trigonometria Considerando o seno x 2/5 determine cosseno X​

Answer 1

A relação fundamental da trigonometria:  $\sin^2 x+\cos^2 x = 1$

Questão:

$(\dfrac{2}{5})^2 +\cos^2x = 1\\\\\\\dfrac{4}{25}+\cos^2x = 1 \\\\\\\cos^2x = 1-\dfrac{4}{25}\\\\\\\cos^2x = \dfrac{21}{25}\\\\\\\cos x = \dfrac{\sqrt{21}}{5}$