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Given cos A = 3/10 and tan A < 0 , find sin A .

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Answer: Since we know that cos A = 3/10, we can use the Pythagorean identity to find sin A:

sin^2 A + cos^2 A = 1

sin^2 A = 1 - cos^2 A

sin A = sqrt(1 - cos^2 A)

Substituting cos A = 3/10, we get:

sin A = sqrt(1 - (3/10)^2)

sin A = sqrt(1 - 9/100)

sin A = sqrt(91)/10

Since we also know that tan A < 0, we know that the sine and tangent of A have opposite signs, and therefore sin A is negative.

Therefore:

sin A = -sqrt(91)/10

Explanation:

User Johari
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