In triangle ABC, angle C is 90 degrees, cosA is equal to √91 / 10. Find cosB

univerkov | September 25, 2021 | education

In a right-angled triangle, the cosine of one acute angle is equal to the sine of the other.

SinABC = CosBAC = √91 / 10.

Sin2ABC + Cos2ABC = 1.

Cos2ABC = 1 – 91/100 = 9/100.

Cos2ABC = 3/10.

Answer: Cos2ABC = 3/10.

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