Math  /  Trigonometry

QuestionGiven the triangle 10.8751710.875 \quad 17, find the measure of angle AA using the Law of Cosines. Picture is not drawn to scale A=A= \square degrees

Studdy Solution

STEP 1

1. The triangle is a non-right triangle.
2. The sides of the triangle are labeled as a=10.875 a = 10.875 , b=17 b = 17 , and c=21.62517 c = 21.62517 .
3. Angle A A is opposite side c c .

STEP 2

1. Recall the Law of Cosines formula.
2. Substitute the given side lengths into the formula.
3. Solve for cosA\cos A.
4. Use the inverse cosine function to find angle A A .

STEP 3

Recall the Law of Cosines formula:
c2=a2+b22abcosA c^2 = a^2 + b^2 - 2ab \cdot \cos A

STEP 4

Substitute the given side lengths into the formula:
(21.62517)2=(10.875)2+(17)22×10.875×17×cosA (21.62517)^2 = (10.875)^2 + (17)^2 - 2 \times 10.875 \times 17 \times \cos A

STEP 5

Calculate the squares of the side lengths:
21.625172=467.625 21.62517^2 = 467.625 10.8752=118.265625 10.875^2 = 118.265625 172=289 17^2 = 289
Substitute these values back into the equation:
467.625=118.265625+2892×10.875×17×cosA 467.625 = 118.265625 + 289 - 2 \times 10.875 \times 17 \times \cos A
Simplify the equation:
467.625=407.265625369.75cosA 467.625 = 407.265625 - 369.75 \cdot \cos A
Rearrange to solve for cosA\cos A:
467.625407.265625=369.75cosA 467.625 - 407.265625 = -369.75 \cdot \cos A
60.359375=369.75cosA 60.359375 = -369.75 \cdot \cos A
cosA=60.359375369.75 \cos A = \frac{60.359375}{-369.75}
cosA0.1633 \cos A \approx -0.1633

STEP 6

Use the inverse cosine function to find angle A A :
A=cos1(0.1633) A = \cos^{-1}(-0.1633)
Calculate angle A A :
A99.4 A \approx 99.4^\circ
The measure of angle A A is:
99.4 \boxed{99.4^\circ}

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