Question

Qual o valor? Por favor responda

Answer 1

$sen^2 \alpha + cos^2\alpha =1$
$(3/5)^2 + cos^2\alpha =1$
$cos^2\alpha =1-(3/5)^2$
$cos^2\alpha =1-(9/25)$
$cos^2\alpha =(25-9)/25$
$cos^2\alpha =(16)/25$
$cos \alpha =\sqrt{(16)/25}$
$cos \alpha =4/5$