In triangle ABC, angle C is straight, BC = 3√21, cosB = 0.4, find AB.
| August 3, 2021 | education
1) ▲ ABC;
∡ С – straight line;
ВС = 3 * √21, cos B = 0.4.
Find AB.
2) cos b = BC / AB;
Let us express AB.
cos b * AB = BC;
AB = BC / cos b;
3) Find AB.
AB = BC / cos b = 3 * √21 / (0.4) = 3 * √21 / (4/10) = 3 * √21 / (2/5) = 3 * √21 * 5/2 = 1 .5 * 5 * √21 = 7.5 * √21;
Answer: AB = 7.5 * √21.
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