In triangle ABC, if AB = 10 cm, AC = 6 cm, and angle A = 30°, what is the length

Practice Questions

Q1
In triangle ABC, if AB = 10 cm, AC = 6 cm, and angle A = 30°, what is the length of side BC?
  1. 8 cm
  2. 7 cm
  3. 5 cm
  4. 4 cm

Questions & Step-by-Step Solutions

In triangle ABC, if AB = 10 cm, AC = 6 cm, and angle A = 30°, what is the length of side BC?
  • Step 1: Identify the sides and angle of triangle ABC. We have AB = 10 cm, AC = 6 cm, and angle A = 30°.
  • Step 2: Recall the Law of Cosines formula: BC² = AB² + AC² - 2 * AB * AC * cos(A).
  • Step 3: Substitute the known values into the formula: BC² = 10² + 6² - 2 * 10 * 6 * cos(30°).
  • Step 4: Calculate the squares: 10² = 100 and 6² = 36.
  • Step 5: Find cos(30°). The value of cos(30°) is √3/2.
  • Step 6: Substitute the values into the equation: BC² = 100 + 36 - 2 * 10 * 6 * (√3/2).
  • Step 7: Simplify the equation: BC² = 100 + 36 - 60√3.
  • Step 8: Combine the numbers: BC² = 136 - 60√3.
  • Step 9: To find BC, take the square root: BC = √(136 - 60√3).
  • Step 10: Use a calculator to approximate the value: BC ≈ 7 cm.
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