The sine of the outer angle at the vertex A of a right-angled triangle ABC with right angle C is 0.4.
| July 23, 2021 | education
The sine of the outer angle at the vertex A of a right-angled triangle ABC with right angle C is 0.4. Find the cosine of angle C
The outer angle BAD is adjacent to the inner angle BAC, the sum of which is 180, then the angle BAC = (180 – BAD).
Determine the sine of the inner angle BAC.
SinBAC = Sin (180 – BAD) = SinBAD = 0.4.
In a right-angled triangle, the sine of one acute angle of the triangle is equal to the cosine of the other acute angle of the triangle, then CosABC = SinBAC = 0.4.
Answer: The cosine of angle B is 0.4.
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