The law of cosines is used to find the value of [tex]\( m \)[/tex].

[tex]\[
\begin{array}{l}
m^2 = 27^2 + 18^2 - 2(27)(18) \cos(280^\circ) \\
m^2 = 729 + 324 - (972) \cos(28^\circ) \\
m^2 = 1053 - (972) \cos(28^\circ)
\end{array}
\][/tex]

To the nearest whole number, what is the value of [tex]\( m \)[/tex]?

A. 13
B. 14
C. 43
D. 45



Answer :

To solve for the value of [tex]\( m \)[/tex] using the Law of Cosines, we follow these steps:

1. State the Law of Cosines formula:
[tex]\[ m^2 = a^2 + b^2 - 2ab \cos(\theta) \][/tex]
Here, [tex]\( a = 27 \)[/tex], [tex]\( b = 18 \)[/tex], and [tex]\( \theta = 28^\circ \)[/tex].

2. Substitute the given values into the formula:
[tex]\[ m^2 = 27^2 + 18^2 - 2 \cdot 27 \cdot 18 \cdot \cos(28^\circ) \][/tex]

3. Calculate the squares of the sides:
[tex]\[ 27^2 = 729 \][/tex]
[tex]\[ 18^2 = 324 \][/tex]

4. Sum the squares:
[tex]\[ 729 + 324 = 1053 \][/tex]

5. Find the cosine of [tex]\( 28^\circ \)[/tex] (using a calculator or a trigonometric table, but let's just consider the given result):
[tex]\[ \cos(28^\circ) \approx 0.882947593 \][/tex]

6. Calculate the product [tex]\( 2 \cdot 27 \cdot 18 \cdot \cos(28^\circ) \)[/tex]:
[tex]\[ 2 \cdot 27 \cdot 18 \cdot 0.882947593 = 972 \cdot 0.882947593 \approx 858.225060258877 \][/tex]

7. Subtract this product from the sum of the squares:
[tex]\[ m^2 = 1053 - 858.225060258877 \approx 194.77493974112292 \][/tex]

8. Take the square root of [tex]\( m^2 \)[/tex] to find [tex]\( m \)[/tex]:
[tex]\[ m = \sqrt{194.77493974112292} \approx 13.95617926730389 \][/tex]

9. Round [tex]\( m \)[/tex] to the nearest whole number:
[tex]\[ m \approx 14 \][/tex]

Therefore, to the nearest whole number, the value of [tex]\( m \)[/tex] is [tex]\( 14 \)[/tex]. The correct answer is:
[tex]\[ \boxed{14} \][/tex]