Question

What is the length x of the side of the triangle below? (Hint: Use the cosine function.)

Answer 1

Answer

The correct answer is A.

Explanation

The given triangle is a right triangle.

The length of the hypotenuse is $2.5$ units.

The given angle is $39\degree$.

The unknown side $x$ is adjacent to the given angle.

We can therefore use the cosine function to find $x$.

Recall the mnemonics CAH.

This means that;

$\cos\theta=\frac{Adjacent}{Hypotenuse}$

This implies that,

$\cos39\degree=\frac{x}{2.5}$

We multiply both sides by $2.5$ to get,

$2.5\cos39\degree=x$

$x=2.5(0.7771)$

We evaluate to get

$x=1.94$

Therefore the length $x$ of the side of the triangle is $1.9$ units to the nearest tenth.