Question

If x = 3, y = 6, then cos e equal to:

Answer 1

The cosine of an angle theta in a right triangle is given by its adjacent side divided by the hypotenuse:

`\cos \theta=(x)/(r)`

We don't know the value of r but with x, y and the Pythagorean Theorem we can find it:

`\begin{gathered} r=\sqrt[]{x^2+y^2}=\sqrt[]{3^2+6^2}=\sqrt[]{9+36}=\sqrt[]{45} \\ r=6.71 \end{gathered}`

Then the cosine we are looking for is:

`\cos \theta=(x)/(r)=(3)/(6.71)=0.45`

Then the correct option is the second one since:

`\frac{\sqrt[]{5}}{5}=0.45`