Use the Law of Cosines, a2=b2+c2−2bc⋅cosA, to find the value of angle A in a right triangle, where a=7, b=24, and c=25.(1 point)

Responses

25.1 degrees
25.1 degrees

73.6 degrees
73.6 degrees

89.9 degrees
89.9 degrees

16.3 degrees
16.3 degrees

1 answer

To find angle \( A \) in the triangle using the Law of Cosines, we can rearrange the formula:

\[ a^2 = b^2 + c^2 - 2bc \cdot \cos A \]

Given:

  • \( a = 7 \)
  • \( b = 24 \)
  • \( c = 25 \)

Plugging these values into the Law of Cosines, we get:

\[ 7^2 = 24^2 + 25^2 - 2 \cdot 24 \cdot 25 \cdot \cos A \]

Calculating the squares:

\[ 49 = 576 + 625 - 1200 \cdot \cos A \]

Calculating \( 24^2 + 25^2 \):

\[ 49 = 1201 - 1200 \cdot \cos A \]

Rearranging the equation to isolate \( \cos A \):

\[ 1200 \cdot \cos A = 1201 - 49 \] \[ 1200 \cdot \cos A = 1152 \] \[ \cos A = \frac{1152}{1200} \] \[ \cos A = 0.96 \]

Now, to find the angle \( A \):

\[ A = \cos^{-1}(0.96) \]

Using a calculator:

\[ A \approx 16.26 \text{ degrees} \]

Rounded to one decimal place, the angle \( A \) is approximately \( 16.3 \) degrees. Therefore, the correct response is:

16.3 degrees.