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What is the value of [tex]n[/tex] to the nearest whole number?

A. 18
B. 22
C. 29
D. 41

Law of cosines: [tex]a^2 = b^2 + c^2 - 2bc \cos(A)[/tex]


Sagot :

To find the value of [tex]\( n \)[/tex] to the nearest whole number, we will apply the Law of Cosines, which states:

[tex]\[ a^2 = b^2 + c^2 - 2 b c \cos(A) \][/tex]

Given the values:
- [tex]\( a = 22 \)[/tex]
- [tex]\( b = 29 \)[/tex]
- [tex]\( c = 41 \)[/tex]
- [tex]\( A = 18^\circ \)[/tex]

First, we need to convert the angle [tex]\( A \)[/tex] from degrees to radians, because the cosine function typically works with radians in mathematical calculations. The conversion from degrees to radians is done using the formula:

[tex]\[ \text{radians} = \text{degrees} \times \frac{\pi}{180} \][/tex]

Therefore, [tex]\( A = 18^\circ \)[/tex] converted to radians is:

[tex]\[ A = 18 \times \frac{\pi}{180} = \frac{\pi}{10} \approx 0.314 \text{ radians} \][/tex]

Applying the Law of Cosines:

[tex]\[ a^2 = b^2 + c^2 - 2 b c \cos(A) \][/tex]

Plugging in the given values:

[tex]\[ 22^2 = 29^2 + 41^2 - 2 \cdot 29 \cdot 41 \cos(0.314) \][/tex]

Calculating the squares:

[tex]\[ 484 = 841 + 1681 - 2 \cdot 29 \cdot 41 \cos(0.314) \][/tex]

Adding the squares:

[tex]\[ 484 = 2522 - 2 \cdot 29 \cdot 41 \cos(0.314) \][/tex]

Now, compute the cosine part. Let's call this value [tex]\( x \)[/tex]:

[tex]\[ x = 2 \cdot 29 \cdot 41 \cos(0.314) \][/tex]

[tex]\[ x \approx 2 \cdot 29 \cdot 41 \cdot 0.951 \approx 2263.262 \][/tex]

Continuing with the equation:

[tex]\[ 484 = 2522 - 2263.262 \][/tex]

Solving this step-by-step:

[tex]\[ 484 = 258.738 \][/tex]

To find the value of [tex]\( n \)[/tex], we solve for [tex]\( n \)[/tex]:

[tex]\[ n^2 = 258.738 \][/tex]

Taking the square root of both sides:

[tex]\[ n = \sqrt{258.738} \approx 16.09 \][/tex]

Therefore, rounding [tex]\( n \)[/tex] to the nearest whole number gives:

[tex]\[ n \approx 16 \][/tex]

Thus, the value of [tex]\( n \)[/tex] to the nearest whole number is:

[tex]\[ \boxed{16} \][/tex]