In a parallelogram ABCD with an acute angle c sinA = 0.28 find cosB
| September 30, 2021 | education
The sum of the adjacent angles of a parallelogram is 1800.
Since SinA = 0.28, then SinB = Sin (180 – A) = SinA = 0.28.
Sin2B + Cos2B = 1.
Cos2B = 1 – 0.282 = 0.9216.
CosB = 0.96.
Since the angle B is obtuse, then CosB = -0.96.
Answer: CosB = -0.96.
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