Triangle DEF contains right angle E. If angle D measures 40° and its adjacent side measures 7.6 units, what is the measure of side EF? Round your answer to the nearest hundredth.

4.89 units
5.34 units
6.38 units
9.06 units

1 answer

To find the length of side EF in triangle DEF, we can use the trigonometric functions related to right triangles.

Given:

  • Angle D = 40°
  • Side DE (adjacent to angle D) = 7.6 units
  • Angle E is the right angle

Since we want to find side EF (which is opposite angle D), we can use the tangent function:

\[ \tan(D) = \frac{\text{opposite}}{\text{adjacent}} \]

Here, the opposite side is EF, and the adjacent side is DE. Thus, we have:

\[ \tan(40°) = \frac{EF}{7.6} \]

To solve for EF, we rearrange the equation:

\[ EF = 7.6 \cdot \tan(40°) \]

Next, we calculate \(\tan(40°)\):

\[ \tan(40°) \approx 0.8391 \]

Now, we can substitute this value into our equation:

\[ EF = 7.6 \cdot 0.8391 \approx 6.38 \text{ units} \]

Thus, the measure of side EF, rounded to the nearest hundredth, is:

\[ \boxed{6.38 \text{ units}} \]