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Question

If cot x = (5/8), then find the value of 7cosx

A 35/√89 Correct Answer Incorrect Answer
B 32/√89 Correct Answer Incorrect Answer
C 30/√89 Correct Answer Incorrect Answer
D 34/√89 Correct Answer Incorrect Answer

Solution

1 + cot2 x = cosec2 x Or, 1 + (5/8)2 = 1 + (25/64) = (89/64) = cosec2 x So, cosec x = (√89/8) Or, sin x = (8/√89) So, cos2 x = 1 - sin2 x So, cos2 x = 1 - (64/89) = (25/89) So, cos x = (5/√89) So, 7cos x = (35/√89)

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