Calculate the third side of a triangle if its two sides are respectively 2 cm and 8 cm, and the angle between them is 60 °.
| February 27, 2021 | education
Using the cosine theorem, we find the third side of the triangle, we have:
c ^ 2 = 2 ^ 2 + 8 ^ 2 – 2 * 2 * 8 * cos60˚ = 4 + 64 – 32 * (1/2) = 68 – 16 = 52.
c = √52 = 2√13 (cm) or c = -√52 = -2√13 – does not satisfy the condition of the problem.
Answer: the third side of the triangle is 2√13 cm.
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