In a triangle two sides are 7 and 8 and the angle between them is . What is the length of the third side?
Answer and explanation
Correct answer: A.
- Step 1: Use the law of cosines: . Step 2. This is , so . **Answer: . Why not the others:** is the right-angle case, uses a plus sign in front of the cosine term, and is the difference of the squares.
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