Question

Use the image to answer the question.

A right triangle has three sides with measures. Left leg, 5 point zero. Right leg, 7 point 7. Hypotenuse, 9 point 2. One interior angle is labeled x degrees.

Use the Law of Cosines equation to solve for the indicated angle x. Round your answer to the nearest tenth.

(1 point)
Responses

x=57.1°
x is equal to 57.1 degrees

x=56°
x is equal to 56 degrees

x=90.3°
x is equal to 90.3 degrees

x=32.9°
x is equal to 32.9 degrees

1 answer

To find angle \( x \) using the Law of Cosines, we can apply the formula:

\[ c^2 = a^2 + b^2 - 2ab \cdot \cos(x) \]

where:

  • \( c \) is the length of the hypotenuse,
  • \( a \) and \( b \) are the lengths of the other two sides.

In your triangle:

  • \( c = 9.2 \) (the hypotenuse),
  • \( a = 5.0 \) (one leg),
  • \( b = 7.7 \) (the other leg).

Plugging in the values:

\[ (9.2)^2 = (5.0)^2 + (7.7)^2 - 2 \cdot (5.0) \cdot (7.7) \cdot \cos(x) \]

Calculating the squares:

\[ 84.64 = 25 + 59.29 - 77 \cdot \cos(x) \]

Now combine the known values:

\[ 84.64 = 84.29 - 77 \cdot \cos(x) \]

Subtract 84.29 from both sides:

\[ 84.64 - 84.29 = -77 \cdot \cos(x) \]

\[ 0.35 = -77 \cdot \cos(x) \]

Now, divide both sides by -77 to isolate \( \cos(x) \):

\[ \cos(x) = \frac{-0.35}{77} \]

Calculating the right side:

\[ \cos(x) \approx -0.004545 \]

To find \( x \), take the arccosine:

\[ x = \cos^{-1}(-0.004545) \]

Using a calculator:

\[ x \approx 90.3° \]

Thus, rounding to the nearest tenth, we find:

x is equal to 90.3 degrees.

So the correct response is:

x=90.3° x is equal to 90.3 degrees