Answer:
[tex]cos\theta=\frac{3}{5}[/tex]
Step-by-step explanation:
Since [tex]sin\theta=0.8[/tex] is the same as [tex]sin\theta=\frac{4}{5}[/tex] and [tex]sin\theta=\frac{opposite}{hypotenuse}[/tex], then we know that the side opposite to the angle [tex]\theta[/tex] is 4 units and the hypotenuse is 5 units.
Because [tex]cos\theta=\frac{adjacent}{hypotenuse}[/tex], then we have to find the adjacent side to the angle [tex]\theta[/tex] using the Pythagorean Theorem:
[tex]a^2+b^2=c^2\\\\(adjacent)^2+(opposite)^2=(hypotenuse)^2\\\\(adjacent)^2+4^2=5^2\\\\(adjacent)^2+16=25\\\\(adjacent)^2=9\\\\adjacent=3[/tex]
Therefore, since the adjacent side is 3 units, then [tex]cos\theta=\frac{3}{5}[/tex]
