a = 5.0

b = 7.7

c = 9.2

Use the Law of Cosines equation to solve for the indicated angle x. Round your answer to the nearest tenth. (1 point) Responses 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 x=57.1°

1 answer

To solve for the angle \( x \) using the Law of Cosines, we will determine which angle we want to calculate. Let's assume that we want to find the angle opposite side \( c \). The Law of Cosines states:

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

Where:

  • \( a = 5.0 \)
  • \( b = 7.7 \)
  • \( c = 9.2 \)

Substituting in the values we have:

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

Calculating each term:

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

Now simplify:

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

Rearranging gives:

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

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

Now isolate \( \cos(x) \):

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

Calculating \( \cos(x) \):

\[ \cos(x) = -0.00454545 \]

Now, to find \( x \), we take the inverse cosine:

\[ x = \cos^{-1}(-0.00454545) \]

Calculating \( x \):

\[ x \approx 90.3^\circ \text{ (taking into account the negative value results in an angle over 90 degrees)} \]

Thus, rounding to the nearest tenth, the answer is:

x is equal to 90.3 degrees.