In a triangle, the two sides are 17cm and 18cm, and the angle between them is 120 degrees.
| April 5, 2021 | education
In a triangle, the two sides are 17cm and 18cm, and the angle between them is 120 degrees. Find the third side of the triangle.
If you know the two sides of the triangle and the angle between them, then you can find the third side by the cosine theorem a ^ 2 = b ^ 2 + c ^ 2 – 2bc * cosα, where α is the angle between sides b and c.
a ^ 2 = 17 ^ 2 + 18 ^ 2 – 2 * 17 * 18 * cos120 ° = 289 + 324 – 612 * (-1/2) = 613 + 306 = 919.
a = √919.
Answer: The third side of the triangle is √919.
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