Find the cosine of the angle A of triangle ABC if BC = 5, AC = 6, AB = 8.
| April 2, 2021 | education
In order to find the cosine of the angle A we use the cosine theorem. For a triangle with sides a, b, c and angle A opposite side a, it is true a ^ 2 = b ^ 2 + c ^ 2-2 * b * c * cosA. Substitute the values of the sides of the triangle: 5 ^ 2 = 8 ^ 2 + 6 ^ 2 + 2 * 8 * 6 * cosA, 25 = 64 + 16 + 96cosA, 96cosA = 55, cosA = 55/96.
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