In triangle ABC, angle C is 90 °, sin A = 3/5. Find cos B.
| July 17, 2021 | education
A triangle in which one angle is 90 ° is called rectangular.
In this calculation, it is necessary to apply the theorems of sines and cosines of angles. Sine is the ratio of the opposite leg to the hypotenuse, and the cosine is the ratio of the adjacent leg to the hypotenuse.
In this way:
sin A = BC / AB;
cos B = BC / AB.
From this it can be seen that the sine of angle A is equal to the cosine of angle B:
sin A = cos B.
Since sin A is equal to 3/5, then cos B is also equal to 3/5.
Answer: The cosine of angle B is 3/5.
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