In triangle , side , and angle . Calculate the length of side .

Answer and explanation

Correct answer: D.

  1. Step 1: State the cosine rule for side : .
  2. Step 2: Substitute the known values, noting that : .
  3. Step 3: Take the square root: .
Answer
.
Why not the others: makes a sign error by subtracting (); simply adds ; uses .

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