In triangle ABC, angle C is 90 degrees, AB = 5, cosA = 0.8. Find BC.
| April 18, 2021 | education
Since the angle is C = 90 °, the triangle ABC is right-angled, then, by the definition of the cosine of the angle, we obtain the equality:
AC = AB * cos (A) = 5 * 0.8 = 4.
Using the Pythagorean theorem, we find the leg BC:
BC = √ (AB) ^ 2 – (AC) ^ 2 = √ (5 ^ 2 – 4 ^ 2 = 3.
Answer: the required leg is equal.
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