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The area of a triangle is 706. Two of the side lengths are 45 and 33 and the included angle is obtuse. Find the measure of the included angle, to the nearest tenth of 
a degree.
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The area of a triangle is 706706. Two of the side lengths are 4545 and 3333 and the included angle is obtuse. Find the measure of the included angle, to the nearest tenth of a a degree.\newlineAnswer:

Full solution

Q. The area of a triangle is 706706. Two of the side lengths are 4545 and 3333 and the included angle is obtuse. Find the measure of the included angle, to the nearest tenth of a a degree.\newlineAnswer:
  1. Calculate Area Formula: To find the measure of the included angle, we can use the formula for the area of a triangle when two sides and the included angle are known: Area=12absin(C)\text{Area} = \frac{1}{2} \cdot a \cdot b \cdot \sin(C), where aa and bb are the side lengths, and CC is the included angle.\newlineGiven that the area is 706706 square units, and the side lengths are 4545 and 3333 units, we can set up the equation:\newline706=124533sin(C)706 = \frac{1}{2} \cdot 45 \cdot 33 \cdot \sin(C)
  2. Set Up Equation: Now, we need to solve for sin(C)\sin(C). First, we multiply 4545 and 3333, and then divide 706706 by the result, and finally multiply by 22 to isolate sin(C)\sin(C) on one side of the equation:\newlinesin(C)=2×70645×33\sin(C) = \frac{2 \times 706}{45 \times 33}
  3. Solve for sin(C): Perform the calculations to find the value of sin(C):\newlinesin(C)=2×70645×33=141214850.951\sin(C) = \frac{2 \times 706}{45 \times 33} = \frac{1412}{1485} \approx 0.951
  4. Find Acute Angle: Since the angle is obtuse, it lies in the second quadrant where sine is positive. We need to find the angle whose sine is approximately 0.9510.951. We use the inverse sine function to find the angle, but since the range of arcsin\arcsin is from π/2-\pi/2 to π/2\pi/2, we need to find the supplement of the angle that arcsin\arcsin would give us because the angle is obtuse.\newlineLet's first find the acute angle whose sine is 0.9510.951:\newlineCacute=arcsin(0.951)C_{\text{acute}} = \arcsin(0.951)
  5. Calculate Acute Angle: Calculate the acute angle using a calculator: Cacutearcsin(0.951)71.8C_{\text{acute}} \approx \arcsin(0.951) \approx 71.8 degrees
  6. Find Obtuse Angle: To find the obtuse angle, we take the supplement of the acute angle: Cobtuse=180CacuteC_{\text{obtuse}} = 180^\circ - C_{\text{acute}}
  7. Calculate Obtuse Angle: Perform the calculation to find the measure of the obtuse angle: Cobtuse=180 degrees71.8 degrees108.2 degreesC_{\text{obtuse}} = 180 \text{ degrees} - 71.8 \text{ degrees} \approx 108.2 \text{ degrees}

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