BCECE Engineering BCECE Engineering Solved Paper-2001

  • question_answer
    The derivative of \[\log (\tan x)\]is equal to:

    A) \[2\text{ }sec\text{ }2x\]             

    B)  \[2\cos ec2x\] 

    C)         \[\sec 2x\]        

    D)         \[\cos ec2x\]

    Correct Answer: B

    Solution :

    Let \[y=\log \,(\tan x)\] On differentiating both sides, w.r.t.\[x,\] we get \[\frac{dy}{dx}=\frac{1}{\tan x}\frac{d}{dx}(\tan x)\]                 \[=\frac{1}{\tan x}{{\sec }^{2}}x=\frac{1}{{{\cos }^{2}}x\frac{\sin x}{\cos x}}\] \[=\frac{2}{\sin 2x}=2\cos ec2x\]


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