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The law of cosines is used to find the measure of [tex]$\angle Q$[/tex].

[tex]\[
\begin{array}{l}
24^2=20^2+34^2-2(20)(34) \cos (Q) \\
576=400+1156-2(20)(34) \cos (Q) \\
576=1556-1360 \cos (Q) \\
-980=-1360 \cos (Q) \\
\cos (Q) = \frac{980}{1360} \\
Q = \cos^{-1} \left( \frac{980}{1360} \right)
\end{array}
\][/tex]

To the nearest whole degree, what is the measure of [tex]$\angle Q$[/tex]?

A. [tex]$44^{\circ}$[/tex]

B. [tex]$49^{\circ}$[/tex]

C. [tex]$54^{\circ}$[/tex]

D. [tex]$59^{\circ}$[/tex]


Sagot :

To find the measure of [tex]\(\angle Q\)[/tex] using the given equation, we can follow these steps in detail:

1. Apply the Law of Cosines:
The formula given is:
[tex]\[ 24^2 = 20^2 + 34^2 - 2 \cdot 20 \cdot 34 \cdot \cos(Q) \][/tex]
Plug in the values:
[tex]\[ 576 = 400 + 1156 - 1360 \cdot \cos(Q) \][/tex]

2. Simplify the Equation:
Combine the known values on the right-hand side:
[tex]\[ 576 = 1556 - 1360 \cdot \cos(Q) \][/tex]

3. Isolate the Cosine Term:
Subtract 1556 from both sides:
[tex]\[ 576 - 1556 = -1360 \cdot \cos(Q) \][/tex]
Simplify:
[tex]\[ -980 = -1360 \cdot \cos(Q) \][/tex]

4. Solve for [tex]\(\cos(Q)\)[/tex]:
Divide both sides by -1360:
[tex]\[ \cos(Q) = \frac{-980}{-1360} \][/tex]
Simplify the fraction:
[tex]\[ \cos(Q) = 0.7205882352941176 \][/tex]

5. Calculate [tex]\(Q\)[/tex]:
Use the inverse cosine function (arccos) to find [tex]\(Q\)[/tex]:
[tex]\[ Q = \arccos(0.7205882352941176) \][/tex]
In radians, this is approximately:
[tex]\[ Q \approx 0.7661460017514758 \text{ radians} \][/tex]

6. Convert from Radians to Degrees:
Convert [tex]\(Q\)[/tex] from radians to degrees:
[tex]\[ Q \approx 43.89693239118214^\circ \][/tex]

7. Round to the Nearest Whole Degree:
Round the angle to the nearest whole degree:
[tex]\[ Q \approx 44^\circ \][/tex]

Thus, the measure of [tex]\(\angle Q\)[/tex] to the nearest whole degree is [tex]\(\boxed{44^\circ}\)[/tex].
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