In triangle ABC, the angle ∠C is 90 °, AC = 4, cos ∠B = 0.6. Find BC.
September 23, 2021 | education
| Given:
ABC – right triangle;
Angle C = 90 °;
AC = 4;
cos b = 0.6;
Find BC.
Solution:
1) sin b = √ (1 – cos ^ 2 b) = √ (1 – 0.6 ^ 2) = √ (1 – 0.36) = √0.64 = 0.8;
2) tg b = sin b / cos b = 0.8 / 0.6 = 8/6 = (4 * 2) / (2 * 3) = 4/3;
3) tg b = BC / AC;
From here we express BC.
BC = AC * tg b;
Substitute the known values into the formula and calculate the BC leg.
BC = 4 * 4/3 = 16/3.
Answer: BC = 16/3.
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