Math Problem Statement

Find the unknown angles in triangle ABC for each triangle that exists. Given B = 158.2°, c = 8.4, b = 14.8.

Solution

To solve for the unknown angles in triangle ABCABC given that:

  • B=158.2B = 158.2^\circ
  • c=8.4c = 8.4
  • b=14.8b = 14.8

we can proceed as follows:

  1. Check for Validity: Since the angle BB is very large (close to 180180^\circ), we first verify that the triangle is valid. In a triangle, the sum of all angles must equal 180180^\circ. This leaves only 21.821.8^\circ for angles AA and CC, combined. This may limit the possible configurations of the triangle.

  2. Use the Law of Sines: We can apply the Law of Sines to find one of the other angles.

    The Law of Sines states: sinAa=sinBb=sinCc\frac{\sin A}{a} = \frac{\sin B}{b} = \frac{\sin C}{c}

    Rearranging to find sinC\sin C: sinC=csinBb\sin C = \frac{c \cdot \sin B}{b}

    Substituting in the values: sinC=8.4sin(158.2)14.8\sin C = \frac{8.4 \cdot \sin(158.2^\circ)}{14.8}

  3. Calculate sin(158.2)\sin(158.2^\circ): sin(158.2)0.3746\sin(158.2^\circ) \approx 0.3746 Plugging this into the equation: sinC=8.40.374614.80.2128\sin C = \frac{8.4 \cdot 0.3746}{14.8} \approx 0.2128

  4. Find CC: Now we take the inverse sine to find CC: Carcsin(0.2128)12.3C \approx \arcsin(0.2128) \approx 12.3^\circ

  5. Calculate Angle AA: Since A+B+C=180A + B + C = 180^\circ, A=180BC=180158.212.39.5A = 180^\circ - B - C = 180^\circ - 158.2^\circ - 12.3^\circ \approx 9.5^\circ

Summary

The angles in triangle ABCABC are approximately:

  • A9.5A \approx 9.5^\circ
  • B=158.2B = 158.2^\circ
  • C12.3C \approx 12.3^\circ

Would you like more details on any of these steps, or do you have any questions?


Here are five related questions for further exploration:

  1. How does the Law of Sines apply to obtuse triangles?
  2. What other methods could be used to solve for unknown angles in a triangle?
  3. How does the triangle change if angle BB were an acute angle?
  4. What happens if the side lengths bb and cc are different?
  5. How would we solve for side aa in this triangle?

Tip: Remember, the sum of the angles in any triangle is always 180180^\circ. This fact can help you check the validity of your answers.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Triangle Properties
Law of Sines

Formulas

sin A / a = sin B / b = sin C / c

Theorems

Law of Sines

Suitable Grade Level

Grades 10-12